Reliability, correctness, and recovery

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Reliability becomes concrete when a failure leaves an obligation unfinished. Follow one accepted order through the failure catalog, identify the durable evidence and retry owner, then work through containment, replay, reconciliation, and regional recovery. FSR names a failure-surface row; RT a retry policy; RCV a recovery boundary; RC a reconciliation control; RBK an operator runbook; DR a disaster-recovery tier. Their thresholds are planning examples whose premises must remain visible.

Evidence notation: C identifies a claim in the claim register, A a dated AWS source, F a foundational source, and CS a finding in the repository case study. The source index supplies the full source details. These labels are lookup aids, not facts to memorize.

Reliability is a chain of evidence, not a collection of retry switches. Start with the end-to-end failure surface; then decide which control prevents, detects, contains, or repairs each failure. Availability and empty failure queues do not prove correct orders, positions, or money (C43,C48; F03,F14).

End-to-end failure surface

The authority column names evidence that survives retries and operator action. The ambiguity column states what the customer may safely be told. A response can apply several control classes, but residual ambiguity remains visible. Retries follow C45 and Featonby/Brooker guidance: deadline, bounded attempts, exponential backoff with full jitter, stable identity, and one owner where possible (F03,F11,F12). Backlog and fairness follow C44,C61 and the queue/SRE controls in F13,F14. Stable business identity and business-effect idempotency remain C40; no holding area alone is repair under C43.

Inference: for this repository, no transport acknowledgement closes the order-to-ledger proof. CS01 through CS12 therefore route to durable authority, containment, and reconciliation; customer state stays pending or unknown until the named proof exists (C48).

Model details · task8 failures

FAILURE|FSR01|Client or API timeout/disconnect before response|Business-command record and authoritative order lookup by client order ID|Customer sees unknown; acceptance may have committed|Canonical fingerprint; atomic IN_PROGRESS and order/outbox write|Timeout rate; duplicate-key lookup; accepted-without-response count|Do not create a second logical order; return pending with lookup token|Client owns one retry within 8 s deadline; maximum 2 attempts with full jitter; then lookup|Return stored result or reconcile command record with order and outbox|Order API on-call; incident lead if unknown exceeds 2 min|One fingerprint maps to one order ID and durable response; no mismatched payload accepted|prevent detect contain repair|CS01 CS02
FAILURE|FSR02|Producer rejection or ambiguous acknowledgement|Outbox state; per-entry producer result; downstream receipt and business authority|Published false true or unknown; customer order remains accepted-pending|Transactional outbox; stable event ID; validate bus and rules|FailedEntryCount and per-entry errors; outbox age; downstream receipt gaps|Keep outbox pending; circuit-open publisher lane without changing order authority|Retry retryable rejected entries for 2 min and 5 attempts; ambiguous result goes to lookup/reconciliation|Republish original identity only when absence is proven or let idempotent consumer absorb duplicate|Messaging owner; order owner after 2 min|Outbox SENT plus downstream receipt or reconciled authority for every accepted event|prevent detect contain repair|CS01 CS03 CS05
FAILURE|FSR03|Batch API partially accepts records|Per-entry request/result correlation and durable producer manifest|Some records accepted and some rejected; batch-level success is unsafe|Stable entry IDs; retain original manifest; size and quota validation|FailedEntryCount; missing result; accepted versus attempted control total|Freeze blind whole-batch retry; isolate failed or unknown entries|Retry only explicit failures within producer deadline; unknown entries reconcile before retry|Compare manifest IDs with log or downstream inbox and repair missing entries|Producer team; incident if manifest incomplete|Attempted equals explicit success plus explicit failure plus resolved unknown in records|prevent detect contain repair|CS03
FAILURE|FSR04|Delivery is delayed duplicated or out of source order|Stable event ID; source aggregate version; authoritative state|Projection may be stale; business authority unchanged|Inbox idempotency; source version; single writer per invariant scope|Duplicate hit rate; version gaps; oldest age; stale rejection count|Park gaps; reject stale events; isolate replay from live lanes|Transport retry stays bounded; duplicate does not repeat effect; gap waits 60 s then repair|Fetch missing authority range or rebuild projection and reconcile totals|Projection owner; domain owner for source gaps|Each version applied once in order or deterministically superseded; watermark reaches authority|prevent detect contain repair|CS06 CS07
FAILURE|FSR05|Poison or incompatible schema event repeatedly fails|Original payload plus envelope; schema ID/version; validation error; producer identity|One lane or key may be blocked; event effect absent|Compatibility tests; envelope validation; size limits; tolerant readers where semantics permit|Error class and event ID; repeated receive count; iterator age by shard or key|Quarantine exact payload; isolate poison key; never drop silently|Non-retryable validation gets zero ordinary retries; fix producer/consumer then canary replay before retention expires|Transform only through a governed repair job with new lineage; reconcile source and target|Schema owner and consuming domain; page on ordered-lane block|Canary and full replay pass current schema; counts and versions reconcile|prevent detect contain repair|CS08 CS10
FAILURE|FSR06|Handler timeout crash or lost acknowledgement|Inbox state; function logs; checkpoint or queue receipt; protected target transaction|Invocation result unknown; side effect may have committed|Atomic inbox plus state change; timeout shorter than lease; checkpoint after commit|Timeouts; errors; age; redelivery; stale IN_PROGRESS lease|Stop concurrency growth; isolate dependency; preserve record|Invoked-handler retry maximum 3 or event age 15 min; pre-invocation path is separate; then quarantine|Lease takeover after evidence; replay original ID; reconcile protected state before closure|Consumer owner; dependency owner when saturation causes timeout|Inbox COMPLETED and target version or external receipt proves one intended effect|prevent detect contain repair|CS04 CS05 CS06
FAILURE|FSR07|Exchange bank or custodian call times out after possible invocation|Provider request ID; effect receipt; provider status; internal intent and ledger state|Customer sees pending-external; never claim failed or retry safely yet|Provider idempotency key; persist intent before call; callback/status lookup|Timeouts; missing receipt age; provider reconciliation break|Open circuit for new optional work; preserve intent; block conflicting command|Ambiguous outcome gets no blind retry; lookup for 5 min then manual/reconciliation queue|Match provider evidence; post conditional forward completion reversal or correcting entries|Payments or trading operations; compliance escalation by SLA|Provider receipt and internal posting agree under one request ID; break closed with evidence|prevent detect contain repair|CS04 CS11
FAILURE|FSR08|DynamoDB conditional contention throttle or one hot key|Conditional-write result; consumed/throttle metrics; item version and transaction cancellation reason|Command may be rejected busy or pending; no assumed commit|Distribute keys where invariant allows; single writer where it does not; bounded transaction|Throttle and conflict rate by table index tenant and key; latency; queue age|Per-key bulkhead; admission control; reserve authority capacity from projections|Retry retryable throttles within 1 s and 4 attempts full jitter; conflict is lookup/re-evaluate not blind retry|Resolve stale state from authority; repair hot-key model only with ordered versioned migration|Owning bounded context; capacity on-call|Conditional version advances once; invariant and ledger control totals remain valid|prevent detect contain repair|CS02 CS04 CS06 CS12
FAILURE|FSR09|Projection gap lag failed rebuild or stale cutover|Authoritative orders executions ledger plus projection watermark and manifest|Customer view is stale with as-of watermark; cannot authorize correction|Versioned projector; gap buffer; isolated blue-green rebuild; side effects suppressed|Lag age; missing version; source versus projection counts and totals|Keep old projection serving with stale banner; pause cutover; protect authority|Replay at governed rate after dependency-ready gate; stop before live SLO or retention risk|Backfill from durable authority; catch up; validate; conditional alias cutover; reconcile|Projection owner; domain owner approves totals|Manifest complete; no gaps; control totals match; watermark at cutover target|prevent detect contain repair|CS06 CS07 CS09 CS11
FAILURE|FSR10|Notification endpoint or client delivery fails|Notification intent; channel provider receipt; customer inbox state|Business action remains authoritative; customer may not have received notice|Durable intent for required notices; channel preference; client catch-up protocol|Delivery failure; age; provider status; notification projection gap|Isolate channel from command path; degrade to in-app status|Retry only within product expiry and channel budget; do not resend expired one-time codes|Regenerate only from authority and policy; record alternate-channel/manual contact|Notification owner; support or compliance for mandatory notice breach|Required notice has policy-accepted receipt or documented exception; business state unchanged|prevent detect contain repair|CS08 CS11
FAILURE|FSR11|Backlog overload retry storm or dependency saturation|Arrival rate; committed service rate; oldest age; per-class queues and capacity budget|Requests may be rejected busy or delayed with explicit estimate|Admission control; queue cap; bulkheads; reserved and maximum concurrency; fairness lanes|Lambda throttles; queue age; iterator age; rejection and wait by tenant key priority|Shed optional work; cap concurrency and replay; open circuit; reserve command and ledger lanes|One owned retry layer; stop when deadline or age consumes recovery margin|Drain only while mu exceeds lambda plus reserve; reconcile dropped expired or deferred work|Incident commander plus owning service and dependency teams|Age returns below SLO; no starvation; all admitted commands resolved; reconciliation clean|prevent detect contain repair|CS08 CS09 CS12
FAILURE|FSR12|Region loss or unsafe failover|Fenced writer epoch; replicated authority; backups exports logs and external evidence|Commands stop or return unavailable until one writer is proven; projections can be stale|Tested DR tiers; IaC; cross-Region evidence; failover fencing; independent backups|Regional health plus business probes; replication lag; writer-epoch conflict; RTO clock|Stop writes; fence old Region; recover dependencies in authority-first order|Restore service within RTO; recover data only to a point whose age and loss are within RPO; no cross-Region blind replay|Replay outbox and projections; reconcile exchange bank custodian and ledger before unrestricted service|Incident commander; command ledger platform and compliance owners|One active epoch; service restored within RTO; recoverable data loss and recovery-point age within RPO; control totals and game-day evidence complete|prevent detect contain repair|CS01 CS08 CS09 CS11

ID	Trigger	Authoritative state/evidence	Ambiguity/customer state	Prevention	Detection signal	Containment	Retry/replay decision and budget	Repair/reconciliation	Owner/escalation	Correctness proof	Controls	CS routes
FSR01	Client or API timeout/disconnect before response	Business-command record and authoritative order lookup by client order ID	Customer sees unknown; acceptance may have committed	Canonical fingerprint; atomic IN_PROGRESS and order/outbox write	Timeout rate; duplicate-key lookup; accepted-without-response count	Do not create a second logical order; return pending with lookup token	Client owns one retry within 8 s deadline; maximum 2 attempts with full jitter; then lookup	Return stored result or reconcile command record with order and outbox	Order API on-call; incident lead if unknown exceeds 2 min	One fingerprint maps to one order ID and durable response; no mismatched payload accepted	prevent detect contain repair	CS01 CS02
FSR02	Producer rejection or ambiguous acknowledgement	Outbox state; per-entry producer result; downstream receipt and business authority	Published false true or unknown; customer order remains accepted-pending	Transactional outbox; stable event ID; validate bus and rules	FailedEntryCount and per-entry errors; outbox age; downstream receipt gaps	Keep outbox pending; circuit-open publisher lane without changing order authority	Retry retryable rejected entries for 2 min and 5 attempts; ambiguous result goes to lookup/reconciliation	Republish original identity only when absence is proven or let idempotent consumer absorb duplicate	Messaging owner; order owner after 2 min	Outbox SENT plus downstream receipt or reconciled authority for every accepted event	prevent detect contain repair	CS01 CS03 CS05
FSR03	Batch API partially accepts records	Per-entry request/result correlation and durable producer manifest	Some records accepted and some rejected; batch-level success is unsafe	Stable entry IDs; retain original manifest; size and quota validation	FailedEntryCount; missing result; accepted versus attempted control total	Freeze blind whole-batch retry; isolate failed or unknown entries	Retry only explicit failures within producer deadline; unknown entries reconcile before retry	Compare manifest IDs with log or downstream inbox and repair missing entries	Producer team; incident if manifest incomplete	Attempted equals explicit success plus explicit failure plus resolved unknown in records	prevent detect contain repair	CS03
FSR04	Delivery is delayed duplicated or out of source order	Stable event ID; source aggregate version; authoritative state	Projection may be stale; business authority unchanged	Inbox idempotency; source version; single writer per invariant scope	Duplicate hit rate; version gaps; oldest age; stale rejection count	Park gaps; reject stale events; isolate replay from live lanes	Transport retry stays bounded; duplicate does not repeat effect; gap waits 60 s then repair	Fetch missing authority range or rebuild projection and reconcile totals	Projection owner; domain owner for source gaps	Each version applied once in order or deterministically superseded; watermark reaches authority	prevent detect contain repair	CS06 CS07
FSR05	Poison or incompatible schema event repeatedly fails	Original payload plus envelope; schema ID/version; validation error; producer identity	One lane or key may be blocked; event effect absent	Compatibility tests; envelope validation; size limits; tolerant readers where semantics permit	Error class and event ID; repeated receive count; iterator age by shard or key	Quarantine exact payload; isolate poison key; never drop silently	Non-retryable validation gets zero ordinary retries; fix producer/consumer then canary replay before retention expires	Transform only through a governed repair job with new lineage; reconcile source and target	Schema owner and consuming domain; page on ordered-lane block	Canary and full replay pass current schema; counts and versions reconcile	prevent detect contain repair	CS08 CS10
FSR06	Handler timeout crash or lost acknowledgement	Inbox state; function logs; checkpoint or queue receipt; protected target transaction	Invocation result unknown; side effect may have committed	Atomic inbox plus state change; timeout shorter than lease; checkpoint after commit	Timeouts; errors; age; redelivery; stale IN_PROGRESS lease	Stop concurrency growth; isolate dependency; preserve record	Invoked-handler retry maximum 3 or event age 15 min; pre-invocation path is separate; then quarantine	Lease takeover after evidence; replay original ID; reconcile protected state before closure	Consumer owner; dependency owner when saturation causes timeout	Inbox COMPLETED and target version or external receipt proves one intended effect	prevent detect contain repair	CS04 CS05 CS06
FSR07	Exchange bank or custodian call times out after possible invocation	Provider request ID; effect receipt; provider status; internal intent and ledger state	Customer sees pending-external; never claim failed or retry safely yet	Provider idempotency key; persist intent before call; callback/status lookup	Timeouts; missing receipt age; provider reconciliation break	Open circuit for new optional work; preserve intent; block conflicting command	Ambiguous outcome gets no blind retry; lookup for 5 min then manual/reconciliation queue	Match provider evidence; post conditional forward completion reversal or correcting entries	Payments or trading operations; compliance escalation by SLA	Provider receipt and internal posting agree under one request ID; break closed with evidence	prevent detect contain repair	CS04 CS11
FSR08	DynamoDB conditional contention throttle or one hot key	Conditional-write result; consumed/throttle metrics; item version and transaction cancellation reason	Command may be rejected busy or pending; no assumed commit	Distribute keys where invariant allows; single writer where it does not; bounded transaction	Throttle and conflict rate by table index tenant and key; latency; queue age	Per-key bulkhead; admission control; reserve authority capacity from projections	Retry retryable throttles within 1 s and 4 attempts full jitter; conflict is lookup/re-evaluate not blind retry	Resolve stale state from authority; repair hot-key model only with ordered versioned migration	Owning bounded context; capacity on-call	Conditional version advances once; invariant and ledger control totals remain valid	prevent detect contain repair	CS02 CS04 CS06 CS12
FSR09	Projection gap lag failed rebuild or stale cutover	Authoritative orders executions ledger plus projection watermark and manifest	Customer view is stale with as-of watermark; cannot authorize correction	Versioned projector; gap buffer; isolated blue-green rebuild; side effects suppressed	Lag age; missing version; source versus projection counts and totals	Keep old projection serving with stale banner; pause cutover; protect authority	Replay at governed rate after dependency-ready gate; stop before live SLO or retention risk	Backfill from durable authority; catch up; validate; conditional alias cutover; reconcile	Projection owner; domain owner approves totals	Manifest complete; no gaps; control totals match; watermark at cutover target	prevent detect contain repair	CS06 CS07 CS09 CS11
FSR10	Notification endpoint or client delivery fails	Notification intent; channel provider receipt; customer inbox state	Business action remains authoritative; customer may not have received notice	Durable intent for required notices; channel preference; client catch-up protocol	Delivery failure; age; provider status; notification projection gap	Isolate channel from command path; degrade to in-app status	Retry only within product expiry and channel budget; do not resend expired one-time codes	Regenerate only from authority and policy; record alternate-channel/manual contact	Notification owner; support or compliance for mandatory notice breach	Required notice has policy-accepted receipt or documented exception; business state unchanged	prevent detect contain repair	CS08 CS11
FSR11	Backlog overload retry storm or dependency saturation	Arrival rate; committed service rate; oldest age; per-class queues and capacity budget	Requests may be rejected busy or delayed with explicit estimate	Admission control; queue cap; bulkheads; reserved and maximum concurrency; fairness lanes	Lambda throttles; queue age; iterator age; rejection and wait by tenant key priority	Shed optional work; cap concurrency and replay; open circuit; reserve command and ledger lanes	One owned retry layer; stop when deadline or age consumes recovery margin	Drain only while mu exceeds lambda plus reserve; reconcile dropped expired or deferred work	Incident commander plus owning service and dependency teams	Age returns below SLO; no starvation; all admitted commands resolved; reconciliation clean	prevent detect contain repair	CS08 CS09 CS12
FSR12	Region loss or unsafe failover	Fenced writer epoch; replicated authority; backups exports logs and external evidence	Commands stop or return unavailable until one writer is proven; projections can be stale	Tested DR tiers; IaC; cross-Region evidence; failover fencing; independent backups	Regional health plus business probes; replication lag; writer-epoch conflict; RTO clock	Stop writes; fence old Region; recover dependencies in authority-first order	Restore service within RTO; recover data only to a point whose age and loss are within RPO; no cross-Region blind replay	Replay outbox and projections; reconcile exchange bank custodian and ledger before unrestricted service	Incident commander; command ledger platform and compliance owners	One active epoch; service restored within RTO; recoverable data loss and recovery-point age within RPO; control totals and game-day evidence complete	prevent detect contain repair	CS01 CS08 CS09 CS11

Every repository defect maps explicitly; a row can improve several classes but must still name what remains ambiguous.

Model details · task8 cs

CSMAP|CS01|FSR01 FSR02 FSR12|Atomic order idempotency and outbox|Outbox age and accepted-without-event manifest|Keep accepted order pending|Replay original event and reconcile order to downstream|An accepted order can remain pending until receipt or reconciliation
CSMAP|CS02|FSR01 FSR08|Fingerprint plus durable result in authority|Mismatched fingerprint and stale IN_PROGRESS age|Reject conflict and return pending|Repair command record against order and outbox|Cached response alone remains non-authoritative
CSMAP|CS03|FSR02 FSR03|Per-entry producer correlation|FailedEntryCount and unknown result count|Do not retry whole batch|Retry explicit failures and reconcile unknowns|Zero failed entries does not prove routing or effect
CSMAP|CS04|FSR06 FSR07 FSR08|Conditional local transaction plus outbox|State transition and publication control totals|Stop conflicting transition|Forward-complete or correct from authority|External execution can remain ambiguous
CSMAP|CS05|FSR02 FSR06|Independent publication intent|Trade-with-unsent-outbox age|Keep publication retryable|Publish original identity and reconcile receipt|Duplicate trade guard alone cannot repair publication
CSMAP|CS06|FSR04 FSR06 FSR08 FSR09|Inbox plus projection mutation|Duplicate hit and stale version metrics|Reject repeated event effect|Rebuild and reconcile projection|Optimistic version alone is not identity
CSMAP|CS07|FSR04 FSR09|Authoritative source sequence|Gap and stale-event counters|Buffer gap and reject stale|Backfill missing versions then cut over|Arrival order remains non-authoritative
CSMAP|CS08|FSR05 FSR10 FSR11 FSR12|Correct queue policy and independent retained source|Failed DLQ writes plus queue and source age|Quarantine and preserve payload|Canary redrive then reconcile|Configured DLQ can still be unwritable or incomplete
CSMAP|CS09|FSR09 FSR11 FSR12|PITR export or complete paginated manifest|Page count export completion and control totals|Do not publish partial snapshot|Re-export and validate before cutover|Asynchronous export is not a transaction snapshot
CSMAP|CS10|FSR05|Exact money schema with currency scale rounding|Schema validation and amount invariant errors|Quarantine unsafe payload|Governed conversion with lineage and balancing proof|Historical floats may require manual evidence
CSMAP|CS11|FSR07 FSR09 FSR10 FSR12|Append-only ledger reservations and reconciliation|Ledger imbalance reservation mismatch and external breaks|Freeze affected account or product scope|Reversal or correcting entry from authority only|Missing historical authority can make exact replay impossible
CSMAP|CS12|FSR08 FSR11|Measured long-lived or serverless capacity choice|Tail latency saturation age and cost per execution|Admission control and dedicated matcher bulkhead|Scale or migrate with ordered drain and reconciliation|Compute choice does not fix domain correctness

CS	Failure routes	Prevent	Detect	Contain	Repair	Residual ambiguity
CS01	FSR01 FSR02 FSR12	Atomic order idempotency and outbox	Outbox age and accepted-without-event manifest	Keep accepted order pending	Replay original event and reconcile order to downstream	An accepted order can remain pending until receipt or reconciliation
CS02	FSR01 FSR08	Fingerprint plus durable result in authority	Mismatched fingerprint and stale IN_PROGRESS age	Reject conflict and return pending	Repair command record against order and outbox	Cached response alone remains non-authoritative
CS03	FSR02 FSR03	Per-entry producer correlation	FailedEntryCount and unknown result count	Do not retry whole batch	Retry explicit failures and reconcile unknowns	Zero failed entries does not prove routing or effect
CS04	FSR06 FSR07 FSR08	Conditional local transaction plus outbox	State transition and publication control totals	Stop conflicting transition	Forward-complete or correct from authority	External execution can remain ambiguous
CS05	FSR02 FSR06	Independent publication intent	Trade-with-unsent-outbox age	Keep publication retryable	Publish original identity and reconcile receipt	Duplicate trade guard alone cannot repair publication
CS06	FSR04 FSR06 FSR08 FSR09	Inbox plus projection mutation	Duplicate hit and stale version metrics	Reject repeated event effect	Rebuild and reconcile projection	Optimistic version alone is not identity
CS07	FSR04 FSR09	Authoritative source sequence	Gap and stale-event counters	Buffer gap and reject stale	Backfill missing versions then cut over	Arrival order remains non-authoritative
CS08	FSR05 FSR10 FSR11 FSR12	Correct queue policy and independent retained source	Failed DLQ writes plus queue and source age	Quarantine and preserve payload	Canary redrive then reconcile	Configured DLQ can still be unwritable or incomplete
CS09	FSR09 FSR11 FSR12	PITR export or complete paginated manifest	Page count export completion and control totals	Do not publish partial snapshot	Re-export and validate before cutover	Asynchronous export is not a transaction snapshot
CS10	FSR05	Exact money schema with currency scale rounding	Schema validation and amount invariant errors	Quarantine unsafe payload	Governed conversion with lineage and balancing proof	Historical floats may require manual evidence
CS11	FSR07 FSR09 FSR10 FSR12	Append-only ledger reservations and reconciliation	Ledger imbalance reservation mismatch and external breaks	Freeze affected account or product scope	Reversal or correcting entry from authority only	Missing historical authority can make exact replay impossible
CS12	FSR08 FSR11	Measured long-lived or serverless capacity choice	Tail latency saturation age and cost per execution	Admission control and dedicated matcher bulkhead	Scale or migrate with ordered drain and reconciliation	Compute choice does not fix domain correctness

Four identities, four stopping boundaries

The failure catalog shows why a single message ID cannot protect the whole journey. A broker may suppress a repeated send while the API accepts a second logical command, or a consumer may recognize a duplicate while a provider call remains unknown. Compare the four identities by the state they protect, how long that evidence survives, and what a competing or stale owner may do.

These controls are cumulative, not substitutes (C40,C47,C90; F02,F08,F11). Safety-critical cells use closed key=value contracts: semicolons separate fields, + means every named item is required together, and the verifier accepts only the row-specific values rendered here. This notation also governs the target-DLQ, DR, and rollback/resume cells below.

Model details · task8 identities

IDENTITY|ID01|transport dedupe|Producer-to-broker transport acceptance inside one named broker scope|Broker deduplication or message identifier|Transport acceptance and suppression state|Retain for the documented window only; expiry reopens transport delivery and never proves business expiry|Broker-local acceptance and dedupe only; non-atomic with handler database and external effect|Concurrent duplicate sends use broker rules; a late send after expiry is a new transport attempt|Outside the window rely on business command identity and handler inbox; lookup authority before repeating an effect|Duplicate sends suppressed only inside named transport scope; acknowledgement and transport IDs never prove one business effect
IDENTITY|ID02|handler inbox idempotency|Consumer and protected effect for one stable business event and effect scope|Stable business event ID plus effect type|PENDING with attemptOwner epoch and leaseUntil; COMPLETED with result or REPAIR_REQUIRED|Retain through source replay dispute and audit horizon; cleanup-only TTL never authorizes a new effect|mode=atomic_single_transaction; writes=inbox+protected_effect; split_commit=forbidden|Conditional create elects one owner epoch; expired leaseUntil permits conditional takeover; fenced completion rejects a stale owner|mode=persisted_intent_before_invocation; resolution=receipt_lookup+reconciliation; terminal=COMPLETED_or_REPAIR_REQUIRED; split_success=not_idempotency_proof|Repeated delivery reads fenced COMPLETED and does not repeat the protected effect
IDENTITY|ID03|business-command fingerprint/result|Command and protected order state/outbox for one client command scope|Client command key plus canonical request fingerprint|IN_PROGRESS with attemptOwner epoch leaseUntil; COMPLETED durable response and order ID; REPAIR_REQUIRED on split ambiguity|Retain through client retry dispute and audit horizon; cleanup-only TTL occurs only after protected evidence outlives replay|Atomic command record protected state and outbox in one authoritative transaction when possible|Conditional create elects one owner epoch; same-key races return in-progress or completed; takeover after leaseUntil is conditional and stale completion is fenced|For another store or external effect persist intent before invocation; receipt lookup and reconciliation decide completion or REPAIR_REQUIRED|Same fingerprint returns same durable result; mismatch is rejected; one fenced owner can complete
IDENTITY|ID04|ledger posting uniqueness|Posting set and ledger legs for one financial obligation and currency scope|Posting set ID plus account leg and currency|Immutable balanced debit and credit postings with original and correcting lineage|Retain for the ledger and audit horizon and never expires independently of ledger evidence|Atomic balanced posting set uniqueness and expected authority/reservation version in one ledger transaction|Conditional uniqueness rejects concurrent posting sets; ledger writer epoch fences stale Region or worker completion|External settlement remains a persisted intent plus receipt lookup and reconciliation; ambiguity uses correcting entry rather than expiring uniqueness|Posting set balances by currency; duplicate key cannot add a second leg; receipt and reconciliation close external evidence

ID	Control	Scope	Key	State	Retention/expiry	Atomicity	Race/takeover/fencing	Non-atomic fallback	Proof
ID01	transport dedupe	Producer-to-broker transport acceptance inside one named broker scope	Broker deduplication or message identifier	Transport acceptance and suppression state	Retain for the documented window only; expiry reopens transport delivery and never proves business expiry	Broker-local acceptance and dedupe only; non-atomic with handler database and external effect	Concurrent duplicate sends use broker rules; a late send after expiry is a new transport attempt	Outside the window rely on business command identity and handler inbox; lookup authority before repeating an effect	Duplicate sends suppressed only inside named transport scope; acknowledgement and transport IDs never prove one business effect
ID02	handler inbox idempotency	Consumer and protected effect for one stable business event and effect scope	Stable business event ID plus effect type	PENDING with attemptOwner epoch and leaseUntil; COMPLETED with result or REPAIR_REQUIRED	Retain through source replay dispute and audit horizon; cleanup-only TTL never authorizes a new effect	mode=atomic_single_transaction; writes=inbox+protected_effect; split_commit=forbidden	Conditional create elects one owner epoch; expired leaseUntil permits conditional takeover; fenced completion rejects a stale owner	mode=persisted_intent_before_invocation; resolution=receipt_lookup+reconciliation; terminal=COMPLETED_or_REPAIR_REQUIRED; split_success=not_idempotency_proof	Repeated delivery reads fenced COMPLETED and does not repeat the protected effect
ID03	business-command fingerprint/result	Command and protected order state/outbox for one client command scope	Client command key plus canonical request fingerprint	IN_PROGRESS with attemptOwner epoch leaseUntil; COMPLETED durable response and order ID; REPAIR_REQUIRED on split ambiguity	Retain through client retry dispute and audit horizon; cleanup-only TTL occurs only after protected evidence outlives replay	Atomic command record protected state and outbox in one authoritative transaction when possible	Conditional create elects one owner epoch; same-key races return in-progress or completed; takeover after leaseUntil is conditional and stale completion is fenced	For another store or external effect persist intent before invocation; receipt lookup and reconciliation decide completion or REPAIR_REQUIRED	Same fingerprint returns same durable result; mismatch is rejected; one fenced owner can complete
ID04	ledger posting uniqueness	Posting set and ledger legs for one financial obligation and currency scope	Posting set ID plus account leg and currency	Immutable balanced debit and credit postings with original and correcting lineage	Retain for the ledger and audit horizon and never expires independently of ledger evidence	Atomic balanced posting set uniqueness and expected authority/reservation version in one ledger transaction	Conditional uniqueness rejects concurrent posting sets; ledger writer epoch fences stale Region or worker completion	External settlement remains a persisted intent plus receipt lookup and reconciliation; ambiguity uses correcting entry rather than expiring uniqueness	Posting set balances by currency; duplicate key cannot add a second leg; receipt and reconciliation close external evidence

Retry policy and amplification

Timeout ownership starts at the caller's deadline and allocates shorter attempt timeouts to each dependency. Use one owned retry layer where possible. Classify errors before retry: retryable means transient and safe under identity; non-retryable means validation, authorization, invariant, or permanent contract failure; ambiguous means invocation or effect may have happened, so query state before another effect. Every policy names maximum attempts and maximum event age, exponential backoff with full jitter, and a stop point (C45; F03,F11,F12).

The Kinesis model 5 failure split remains binding: Kinesis/Lambda pre-invocation inability can be bounded by source expiry or maximum event age but not invoked-handler retry count, while invoked-handler errors can additionally use the attempt budget (C76; A98, retrieved 2026-08-22). Step Functions Standard workflow execution is its documented scope; the external effect boundary still needs receipt, provider status lookup, idempotency, compensation where meaningful, and reconciliation (C65; A26, retrieved 2026-08-22). SQS redrive policy is separately bounded by C103; it never expands an attempt budget into permission to repeat an ambiguous effect.

Inference: repository commands use one caller retry inside an 8 s deadline; publishers own broker retry; consumers own invoked-handler retry. At ambiguity, retry stops for lookup or reconciliation rather than multiplying effects (C45,C65,C76; F11,F12; A98, retrieved 2026-08-22).

Model details · task8 retries

RETRY|RT01|retryable producer rejection|Outbox relay|2 min publish deadline|2 s attempt timeout|Maximum 5 attempts and outbox age 2 min|Exponential backoff with full jitter|Keep PENDING then page and reconcile|Per-entry success plus downstream receipt
RETRY|RT02|non-retryable validation or invariant failure|Domain handler|Immediate classification|No dependency retry|Maximum 1 attempt and zero replay until corrected|None|Quarantine with reason; reject customer command or governed repair|Original payload reason and conditional state unchanged
RETRY|RT03|ambiguous external effect|Exchange or bank adapter|5 min lookup deadline|1 s status lookup timeout|Maximum 5 lookups; no blind effect retry|Exponential backoff with full jitter|Manual resolution and reconciliation after lookup budget|Provider receipt agrees with internal intent and ledger
RETRY|RT04|pre-invocation Kinesis Lambda inability|Platform event-source owner|Before source retention and business age budget|Invocation platform owns timeout|Maximum event age bounds path; maximum attempts does not|Service retry plus operator containment|Restore capacity or route retained full payload before expiry|Checkpoint advances only after committed handler result
RETRY|RT05|invoked-handler timeout crash or Step Functions task failure|Consumer or workflow owner|15 min business deadline|Handler timeout shorter than source lease or state timeout|Maximum 3 handler attempts and maximum event age 15 min|Exponential backoff with full jitter|Quarantine or Catch; lookup external effect before retry|Inbox or effect receipt plus workflow history and reconciliation

ID	Class	Owner	Deadline	Timeout	Attempts/age	Backoff	Stop/action	Proof
RT01	retryable producer rejection	Outbox relay	2 min publish deadline	2 s attempt timeout	Maximum 5 attempts and outbox age 2 min	Exponential backoff with full jitter	Keep PENDING then page and reconcile	Per-entry success plus downstream receipt
RT02	non-retryable validation or invariant failure	Domain handler	Immediate classification	No dependency retry	Maximum 1 attempt and zero replay until corrected	None	Quarantine with reason; reject customer command or governed repair	Original payload reason and conditional state unchanged
RT03	ambiguous external effect	Exchange or bank adapter	5 min lookup deadline	1 s status lookup timeout	Maximum 5 lookups; no blind effect retry	Exponential backoff with full jitter	Manual resolution and reconciliation after lookup budget	Provider receipt agrees with internal intent and ledger
RT04	pre-invocation Kinesis Lambda inability	Platform event-source owner	Before source retention and business age budget	Invocation platform owns timeout	Maximum event age bounds path; maximum attempts does not	Service retry plus operator containment	Restore capacity or route retained full payload before expiry	Checkpoint advances only after committed handler result
RT05	invoked-handler timeout crash or Step Functions task failure	Consumer or workflow owner	15 min business deadline	Handler timeout shorter than source lease or state timeout	Maximum 3 handler attempts and maximum event age 15 min	Exponential backoff with full jitter	Quarantine or Catch; lookup external effect before retry	Inbox or effect receipt plus workflow history and reconciliation

The shared planning model below is canonical in research/cost-model.md. Values are illustrative inputs, not quotas or promises.

The input domain requires recovery_capacity_rps > 0 records/s; zero or negative total capacity is rejected before any capacity-share division, while zero-spare and negative-spare fixtures retain positive total capacity.

Model details · task8 chapter results

TASK8_RESULT|nested_retry_worst_case_attempts|27.0
TASK8_RESULT|nested_retry_sensitivity_attempts|64.0
TASK8_RESULT|base_concurrency|24.0
TASK8_RESULT|planned_concurrency|36
TASK8_RESULT|slow_dependency_planned_concurrency|72
TASK8_RESULT|raw_spare_rps|200.0
TASK8_RESULT|effective_redrive_rps|200.0
TASK8_RESULT|recovery_status|POSITIVE_DRAIN
TASK8_RESULT|backlog_growth_rps|0
TASK8_RESULT|backlog_drain_seconds|4500.0
TASK8_RESULT|backlog_drain_minutes|75.0
TASK8_RESULT|recovery_action|bounded replay
TASK8_RESULT|live_capacity_percent|62.5
TASK8_RESULT|replay_capacity_percent|25.0
TASK8_RESULT|safety_capacity_percent|12.5

Kind	Name	Value or equation	Unit
INPUT	retry_layers	3	ratio/count
INPUT	attempts_per_layer	3	ratio/count
INPUT	sensitivity_attempts_per_layer	4	ratio/count
INPUT	arrival_rps	200	records/s
INPUT	service_time_seconds	0.12	s
INPUT	headroom_ratio	1.50	ratio/count
INPUT	slow_service_multiplier	2	ratio/count
INPUT	backlog_records	900000	records
INPUT	recovery_capacity_rps	800	records/s
INPUT	live_arrival_rps	500	records/s
INPUT	safety_reservation_rps	100	records/s
INPUT	replay_rate_cap_rps	200	records/s
FORMULA	nested_retry	attempts_per_layer ^ retry_layers	attempts
FORMULA	concurrency	ceil(arrival_rps * service_time_seconds * headroom_ratio)	concurrent requests
FORMULA	raw_spare	recovery_capacity_rps - live_arrival_rps - safety_reservation_rps	records/s
FORMULA	effective_replay	max(0, min(replay_rate_cap_rps, raw_spare_rps))	records/s
FORMULA	drain_time	if effective_redrive_rps > 0 then backlog_records / effective_redrive_rps else infinite	s
FORMULA	negative_branch	if raw_spare_rps < 0 then backlog_growth_rps = -raw_spare_rps	records/s
RESULT	nested_retry_worst_case_attempts	27	attempts
RESULT	nested_retry_sensitivity_attempts	64	attempts
RESULT	base_concurrency	24	concurrent requests
RESULT	planned_concurrency	36	concurrent requests
RESULT	slow_dependency_planned_concurrency	72	concurrent requests
RESULT	raw_spare_rps	200	records/s
RESULT	effective_redrive_rps	200	records/s
RESULT	recovery_status	POSITIVE_DRAIN	state
RESULT	backlog_growth_rps	0	records/s
RESULT	backlog_drain_seconds	4500	s
RESULT	backlog_drain_minutes	75	min
RESULT	recovery_action	bounded replay	action
RESULT	live_capacity_percent	62.50	%
RESULT	replay_capacity_percent	25	%
RESULT	safety_capacity_percent	12.50	%

Nested retry worst case is 3^3 = 27 attempts; the four-attempt sensitivity is 4^3 = 64. Concurrency rounds up: ceil(200 requests/s × 0.12 s × 1.5) = 36 concurrent requests; a doubled service time needs ceil(72) = 72. Here raw_spare = 800 - 500 - 100 = 200 records/s, effective replay = max(0, min(200, 200)) = 200 records/s, and 900,000 / 200 = 4,500 s = 75 min. At raw_spare = 0, replay is zero and drain time is infinite; at raw_spare < 0, replay is zero, backlog grows at -raw_spare records/s, and operators reduce admission or restore capacity. Of measured 800 records/s capacity, live, replay, and safety use 62.5%, 25%, and 12.5%. A replay/live-traffic capacity split is an admission decision; if measured commit rate falls, reduce replay before live SLOs fail.

Overload containment

Bulkheads isolate failure domains. Reserved concurrency protects and bounds one function; maximum concurrency caps one SQS event-source mapping. Their sums and downstream capacity must agree (C104; Lambda concurrency, A117, retrieved 2026-08-22). A circuit breaker stops calls to a failing dependency but does not repair an unknown effect. Load shedding drops or degrades optional work; admission control rejects before accepting an obligation; a queue cap bounds stored debt. Per-tenant, per-key, and priority lanes provide fairness and dependency isolation. Autoscaling may add capacity, but is distinct from these controls (C44,C61; F03,F13,F14).

Inference: reserve command and ledger capacity first, cap projectors and replay independently, and shed notifications/analytics before financial authority. This allocation is workload policy, not Lambda behavior (C44,C61,C104; F13,F14; A117, retrieved 2026-08-22).

Metrics must be actionable: oldest age above 60 s for orders pages the command owner; replay consuming more than 25% of measured commit capacity aborts replay; any tenant above its configured share is throttled while quiet lanes retain a minimum allocation. These thresholds are planning inputs, not AWS guarantees.

Boundary-specific quarantine and replay

Once overload is contained, choose recovery from the evidence actually retained at the failed boundary. An EventBridge target DLQ, bus archive, SQS processing DLQ, and Kinesis failure destination do not mean the same thing. Read each row from retained payload through readiness, pacing, and validation; the final column identifies when replay is no longer possible from that source.

There is no generic “the DLQ.” An EventBridge target DLQ is an SQS Standard queue holding failed target deliveries; it is distinct from an EventBridge archive, whose replay returns selected events to the source bus where rules can match again (C57,C62; A81,A84, retrieved 2026-08-22). SNS subscription delivery, SQS source processing, Lambda event-source mapping, Kinesis retention, DynamoDB Streams, and Firehose destination delivery also retain different evidence and have different permissions, age, and ordering behavior (C43,C62-C64,C66,C76; A84,A86,A98, retrieved 2026-08-22). SQS managed redrive moves messages without filtering or modification; operators set a bounded velocity and retention must account for Standard versus FIFO timestamp behavior (C103; A118, retrieved 2026-08-22). SQS visibility and acknowledgement remain lease boundaries under C63, even during recovery.

Inference: replay starts only after a dependency-readiness gate, dry run, canary, rate limit, and idempotency proof. Completion means post-replay business validation, not an empty holding area (C43,C103; A118, retrieved 2026-08-22).

Model details · task8 recovery boundaries

BOUNDARY|RCV01|EventBridge target DLQ using SQS Standard; C57 A81 retrieved 2026-08-22|payload=full_event; failure_metadata=RULE_ARN+TARGET_ARN+ERROR_CODE+ERROR_MESSAGE+RETRY_ATTEMPTS+EXHAUSTED_CONDITION; reconstruction=forbidden|Rule-scoped SQS policy for events.amazonaws.com plus consumer read delete and KMS access|SQS retention exceeds incident diagnosis repair and canary window|source_bus_replay=forbidden; recovery=controlled_direct-target_or_repair_consumer_for_failed_TARGET_ARN; ack_delete=after_committed_target_repair+target_receipt+business_reconciliation|Failed target dependency healthy; direct-target contract and consumer inbox proven|Poll under measured target budget; pause before live target SLO breach|Original event ID failed TARGET_ARN and target-specific inbox or intent receipt|No-effect validation then one event or 1 percent canary against failed target|Target receipt and business reconciliation precede SQS delete acknowledgement|Impossible after DLQ expiry without archive or authoritative regeneration
BOUNDARY|RCV02|EventBridge archive replay; C62 A84 retrieved 2026-08-22|Selected full source-bus events retained by archive pattern and time window|Archive replay operator permissions and reviewed optional rule selection|Archive retention exceeds detection fix replay and reconciliation window|Replay goes only to source-bus and may reorder; enumerate every re-matched rule and target; prove idempotency and bound duplicate effects before replay|All selected rules targets consumers and external-effect protections healthy|Narrow UTC window and optional rule set; cancel on duplicate-effect or live SLO budget|Original event ID plus inbox intent and receipt at every re-matched target|Dry run inventory of matched rules and targets then narrow-window canary|DescribeReplay progress plus per-target receipts and business reconciliation|Impossible after archive expiry or when archive pattern omitted the event
BOUNDARY|RCV03|SQS source DLQ and managed redrive; C63 C103 A85 A118 retrieved 2026-08-22|Full SQS message body attributes and receive history available at queue boundary|Redrive IAM and KMS access; RedriveAllowPolicy limits source queues|DLQ retention covers original age; Standard expiry uses original enqueue timestamp|Standard order is best effort; FIFO DLQ movement can break source group order|Consumer fix deployed; dependency capacity and queue policy proven|Start 10 messages/s then ramp below reserved replay share|Stable business ID and atomic inbox|Dry-run parser then one message group or 1 percent canary|Source queue age falls; inbox effects and reconciliation totals match|Impossible after message expiry unless durable authority can regenerate
BOUNDARY|RCV04|Lambda Kinesis on-failure S3 destination; C76 A98 retrieved 2026-08-22|Complete failed invocation record and payload in S3|Lambda destination write plus operator read KMS and lifecycle permissions|S3 lifecycle exceeds Kinesis expiry and investigation SLA|Custom replay restores source key and version; arrival order is not recovered automatically|Handler fix and all downstream dependencies healthy|Separate replay stream or queue at 25 percent measured capacity|Original event ID source version and inbox|Offline parse and no-effect mode then one shard-key canary|S3 manifest IDs equal completed inbox or explained quarantine IDs|Impossible when only SQS or SNS failure metadata exists and source record expired
BOUNDARY|RCV05|Kinesis retained stream replay; C74 C76 A98 retrieved 2026-08-22|Full retained records within configured stream retention|Consumer IAM and checkpoint control isolated from live application|Retention exceeds detection fix drain and margin|Per-shard sequence retained; cross-shard order never inferred|Consumer version compatible and sink has replay lane|Dedicated consumer capped so live traffic and sink stay inside budget|Event ID aggregate version conditional apply|Start from narrow sequence window with side effects disabled|Checkpoint watermark version gaps and control totals reconcile|Impossible after retention expiry without S3 or authoritative backfill
BOUNDARY|RCV06|DynamoDB Streams CDC; C84 A102 retrieved 2026-08-22|Configured key and image fields for 24-hour stream record window|Stream read role and consumer checkpoint access|Fixed 24-hour Streams boundary requires independent longer recovery source|Per-item modification order only; transaction records can interleave|Projection fix deployed and target isolated|Backfill from PITR export or authority; catch-up stream rate capped|Semantic outbox ID or item version plus inbox|Blue-green target dry run and sampled item comparison|Manifest totals versions and final watermark match authority|Impossible from Streams alone after 24 hours or when view omitted needed attributes
BOUNDARY|RCV07|SNS subscription DLQ; C64 A86 retrieved 2026-08-22|Undelivered subscription message in SQS plus endpoint context|SNS topic to SQS policy and redrive operator permissions|Queue retention covers product notice expiry and investigation|Standard delivery can duplicate or reorder; FIFO scope remains subscription-specific|Endpoint and credentials healthy; notice still meaningful|Channel-specific replayer under provider quota|Notification intent ID and expiry check|Render-only dry run then test recipient canary|Provider receipt or documented policy exception; no business state mutation|Impossible or prohibited after notice expiry or missing consent
BOUNDARY|RCV08|Data Firehose S3 backup or failed-delivery objects; C66 A88 retrieved 2026-08-22|Destination-specific buffered records and error output when configured|Firehose delivery role S3 KMS and replay job permissions|S3 lifecycle covers destination repair and audit window|Buffered delivery and retry can duplicate; no business order inferred|Destination schema quota and credentials healthy|New ingestion path isolated and rate-limited below destination headroom|Stable record ID and idempotent destination merge|Validate file schema and sample partition before bounded load|Object manifest row counts destination totals and rejected rows reconcile|Impossible when backup mode omitted the failed payload and source retention expired

ID	Service boundary	Retained	Permissions	Age/retention	Ordering effects	Dependency readiness	Rate limiter	Idempotency	Dry run/canary	Post-replay validation	Replay impossible
RCV01	EventBridge target DLQ using SQS Standard; C57 A81 retrieved 2026-08-22	payload=full_event; failure_metadata=RULE_ARN+TARGET_ARN+ERROR_CODE+ERROR_MESSAGE+RETRY_ATTEMPTS+EXHAUSTED_CONDITION; reconstruction=forbidden	Rule-scoped SQS policy for events.amazonaws.com plus consumer read delete and KMS access	SQS retention exceeds incident diagnosis repair and canary window	source_bus_replay=forbidden; recovery=controlled_direct-target_or_repair_consumer_for_failed_TARGET_ARN; ack_delete=after_committed_target_repair+target_receipt+business_reconciliation	Failed target dependency healthy; direct-target contract and consumer inbox proven	Poll under measured target budget; pause before live target SLO breach	Original event ID failed TARGET_ARN and target-specific inbox or intent receipt	No-effect validation then one event or 1 percent canary against failed target	Target receipt and business reconciliation precede SQS delete acknowledgement	Impossible after DLQ expiry without archive or authoritative regeneration
RCV02	EventBridge archive replay; C62 A84 retrieved 2026-08-22	Selected full source-bus events retained by archive pattern and time window	Archive replay operator permissions and reviewed optional rule selection	Archive retention exceeds detection fix replay and reconciliation window	Replay goes only to source-bus and may reorder; enumerate every re-matched rule and target; prove idempotency and bound duplicate effects before replay	All selected rules targets consumers and external-effect protections healthy	Narrow UTC window and optional rule set; cancel on duplicate-effect or live SLO budget	Original event ID plus inbox intent and receipt at every re-matched target	Dry run inventory of matched rules and targets then narrow-window canary	DescribeReplay progress plus per-target receipts and business reconciliation	Impossible after archive expiry or when archive pattern omitted the event
RCV03	SQS source DLQ and managed redrive; C63 C103 A85 A118 retrieved 2026-08-22	Full SQS message body attributes and receive history available at queue boundary	Redrive IAM and KMS access; RedriveAllowPolicy limits source queues	DLQ retention covers original age; Standard expiry uses original enqueue timestamp	Standard order is best effort; FIFO DLQ movement can break source group order	Consumer fix deployed; dependency capacity and queue policy proven	Start 10 messages/s then ramp below reserved replay share	Stable business ID and atomic inbox	Dry-run parser then one message group or 1 percent canary	Source queue age falls; inbox effects and reconciliation totals match	Impossible after message expiry unless durable authority can regenerate
RCV04	Lambda Kinesis on-failure S3 destination; C76 A98 retrieved 2026-08-22	Complete failed invocation record and payload in S3	Lambda destination write plus operator read KMS and lifecycle permissions	S3 lifecycle exceeds Kinesis expiry and investigation SLA	Custom replay restores source key and version; arrival order is not recovered automatically	Handler fix and all downstream dependencies healthy	Separate replay stream or queue at 25 percent measured capacity	Original event ID source version and inbox	Offline parse and no-effect mode then one shard-key canary	S3 manifest IDs equal completed inbox or explained quarantine IDs	Impossible when only SQS or SNS failure metadata exists and source record expired
RCV05	Kinesis retained stream replay; C74 C76 A98 retrieved 2026-08-22	Full retained records within configured stream retention	Consumer IAM and checkpoint control isolated from live application	Retention exceeds detection fix drain and margin	Per-shard sequence retained; cross-shard order never inferred	Consumer version compatible and sink has replay lane	Dedicated consumer capped so live traffic and sink stay inside budget	Event ID aggregate version conditional apply	Start from narrow sequence window with side effects disabled	Checkpoint watermark version gaps and control totals reconcile	Impossible after retention expiry without S3 or authoritative backfill
RCV06	DynamoDB Streams CDC; C84 A102 retrieved 2026-08-22	Configured key and image fields for 24-hour stream record window	Stream read role and consumer checkpoint access	Fixed 24-hour Streams boundary requires independent longer recovery source	Per-item modification order only; transaction records can interleave	Projection fix deployed and target isolated	Backfill from PITR export or authority; catch-up stream rate capped	Semantic outbox ID or item version plus inbox	Blue-green target dry run and sampled item comparison	Manifest totals versions and final watermark match authority	Impossible from Streams alone after 24 hours or when view omitted needed attributes
RCV07	SNS subscription DLQ; C64 A86 retrieved 2026-08-22	Undelivered subscription message in SQS plus endpoint context	SNS topic to SQS policy and redrive operator permissions	Queue retention covers product notice expiry and investigation	Standard delivery can duplicate or reorder; FIFO scope remains subscription-specific	Endpoint and credentials healthy; notice still meaningful	Channel-specific replayer under provider quota	Notification intent ID and expiry check	Render-only dry run then test recipient canary	Provider receipt or documented policy exception; no business state mutation	Impossible or prohibited after notice expiry or missing consent
RCV08	Data Firehose S3 backup or failed-delivery objects; C66 A88 retrieved 2026-08-22	Destination-specific buffered records and error output when configured	Firehose delivery role S3 KMS and replay job permissions	S3 lifecycle covers destination repair and audit window	Buffered delivery and retry can duplicate; no business order inferred	Destination schema quota and credentials healthy	New ingestion path isolated and rate-limited below destination headroom	Stable record ID and idempotent destination merge	Validate file schema and sample partition before bounded load	Object manifest row counts destination totals and rejected rows reconcile	Impossible when backup mode omitted the failed payload and source retention expired

Ordering and concurrency repair

Order is enforced at the smallest invariant scope, not inferred from arrival. Every mutation carries a source version or sequence, has single-writer ownership for that scope, and uses conditional expected-version apply. A gap buffer has a gap timeout; late, stale, and duplicate policy is deterministic. Backfill runs in an isolated lane and reconciliation proves convergence (C34,C40,C41,C72,C74,C84,C93; F01,F02; A102, retrieved 2026-08-22).

Inference: account/order aggregates serialize only their own invariants; cross-aggregate projections merge deterministically and reconcile rather than claiming global arrival order (C34,C41,C93; F01).

Model details · task8 ordering

ORDERING|OR01|Order state machine|orderVersion monotonic integer|Order command service owns writes|Condition current version equals n then write n plus 1|Buffer missing n for 60 s then fetch authority|Duplicate returns stored result; stale rejected; concurrent conflict re-reads and re-evaluates|No in-place backfill; replay original IDs in order scope|Accepted order and transition manifest by version|Exactly one valid transition occupies each committed version
ORDERING|OR02|Execution and ledger posting set|execution sequence plus postingSetId|Execution authority emits; ledger authority posts|Unique posting legs and expected reservation version in one transaction|Gap blocks affected account only and pages after 30 s|Duplicate is no-op; conflicting fill goes to deterministic break workflow|Replay into isolated ledger validator before any posting|Executions quantities reservations and balanced currency totals|Every execution maps to one balanced posting set or explicit open break
ORDERING|OR03|Portfolio projection|authoritative account-instrument version|Projector lane single-writes each projection key|Inbox ID and expected projection version applied atomically|Gap buffer 60 s then source backfill; never skip silently|Late stale duplicate rejected; same-version different fingerprint quarantined|Blue-green rebuild with effects disabled and rate cap|Compare quantity cost basis and watermark to executions and ledger|Serving alias moves only when manifest complete and totals match
ORDERING|OR04|Kinesis producer key|domain version plus returned same-client sequence when usable|One producer owner per logical key or fenced epoch|Consumers validate domain version regardless of shard sequence|Ambiguous producer acknowledgement breaks sequence chain and triggers lookup|Duplicate identity absorbed; deterministic version wins only from authority|Replay preserves partition key but uses isolated consumer and source-version checks|Checkpoint sequence version-gap and downstream totals|Per-key history is complete without inferring cross-shard order

ID	Scope	Source version	Single writer	Conditional apply	Gap policy	Late/conflict policy	Replay/backfill	Reconciliation	Proof
OR01	Order state machine	orderVersion monotonic integer	Order command service owns writes	Condition current version equals n then write n plus 1	Buffer missing n for 60 s then fetch authority	Duplicate returns stored result; stale rejected; concurrent conflict re-reads and re-evaluates	No in-place backfill; replay original IDs in order scope	Accepted order and transition manifest by version	Exactly one valid transition occupies each committed version
OR02	Execution and ledger posting set	execution sequence plus postingSetId	Execution authority emits; ledger authority posts	Unique posting legs and expected reservation version in one transaction	Gap blocks affected account only and pages after 30 s	Duplicate is no-op; conflicting fill goes to deterministic break workflow	Replay into isolated ledger validator before any posting	Executions quantities reservations and balanced currency totals	Every execution maps to one balanced posting set or explicit open break
OR03	Portfolio projection	authoritative account-instrument version	Projector lane single-writes each projection key	Inbox ID and expected projection version applied atomically	Gap buffer 60 s then source backfill; never skip silently	Late stale duplicate rejected; same-version different fingerprint quarantined	Blue-green rebuild with effects disabled and rate cap	Compare quantity cost basis and watermark to executions and ledger	Serving alias moves only when manifest complete and totals match
OR04	Kinesis producer key	domain version plus returned same-client sequence when usable	One producer owner per logical key or fenced epoch	Consumers validate domain version regardless of shard sequence	Ambiguous producer acknowledgement breaks sequence chain and triggers lookup	Duplicate identity absorbed; deterministic version wins only from authority	Replay preserves partition key but uses isolated consumer and source-version checks	Checkpoint sequence version-gap and downstream totals	Per-key history is complete without inferring cross-shard order

Financial reconciliation control

Replay proves that records were presented again. Reconciliation asks whether the resulting obligations and exact amounts agree with independent authority. Use the next controls to compare the order, execution, ledger, provider, and projection sets for one declared window, then trace any difference through the break lifecycle without treating ownership of a break as successful completion.

Reconciliation is a scheduled and incident-triggered financial control, not a dashboard afterthought. Every internal manifest uses the mandatory UTC [startInclusive,endExclusive) invariant; adjacent windows share the exact endpoint, an event at start is included, and an event at end belongs only to the next window. A run has an immutable manifest: control ID, source versions, timezone, currency/scale, object checksums, record counts, high-water marks, code/config version, and rerun lineage. Provider evidence retains its local business date, timezone, cutoff calendar, and deterministic mapping to the UTC half-open interval. Windows close only when all source watermarks reach or exceed the exclusive end boundary. Control totals retain exact units; counts never substitute for money or quantity (C46-C48,C91; F08,F14-F17). The error-budget and incident practices in F14,F15,F16 govern timeliness, while financial closure still requires the domain evidence below.

Inference: orders, executions, ledger/reservations, and external statements authorize corrections in their owned domains. Portfolio, search, and notification projections only reveal or receive repair; they never authorize money, quantity, or order corrections (C46,C47,C48,C91; F08,F17).

Model details · task8 recon

RECON|RC01|Accepted orders|Authoritative order command store|Order IDs and terminal-state version|UTC [startInclusive,endExclusive); adjacent windows share endpoint; start included and end excluded|Count of accepted orders and exact ordered quantity in instrument units|Accepted IDs versus execution pending rejected canceled partition|Maximum orderVersion and ingestion timestamp reaches exclusive window end|Order operations; 2 min intraday accepted-without-route SLA|Repair outbox or conditional order state only from command evidence|Every accepted ID has one classified lifecycle state and manifest checksum
RECON|RC02|Executions|Execution venue receipts and internal execution authority|Execution IDs venue IDs order IDs and event sequence|UTC [startInclusive,endExclusive); adjacent windows share endpoint; venue local timestamp maps to UTC before comparison|Fill count and exact fill quantity per instrument; exact price in currency minor units with scale|Internal executions versus accepted orders and venue fills|Venue sequence plus internal execution watermark reaches exclusive window end|Trading operations; 1 min duplicate or missing fill SLA|Import missing receipt or mark break; never invent a fill from portfolio|One-to-one venue receipt lineage and no duplicate execution ID
RECON|RC03|Ledger balances and reservations|Append-only balanced ledger and reservation authority|Posting-set IDs account IDs currencies effective times and ledger versions|UTC [startInclusive,endExclusive); adjacent windows share endpoint; effective timestamps use governed UTC|Debit and credit minor units by currency; posting count; balance and reservation minor units|Debits equal credits per currency; executions equal postings; available equals balance minus reservations by policy|Ledger sequence and posting effective-time watermark reaches exclusive window end|Ledger operations; zero imbalance tolerance and 5 min reservation mismatch SLA|Conditional reversal or correcting entries with original-posting lineage; never update history|Balanced totals reservation invariant and independent rerun checksum
RECON|RC04|Exchange custodian and bank evidence|Signed or controlled provider reports API receipts and statements|Provider file IDs checksums accounts and statement sequence|UTC [startInclusive,endExclusive); adjacent windows share endpoint; provider local business date timezone cutoff calendar retained and deterministic mapping recorded|Exchange fill count and quantity; custodian position quantity; bank cash minor units by currency|Provider totals versus executions ledger cash and settled positions|Provider statement complete marker and internal watermark reaches mapped exclusive end|Trading payments or settlement operations; product-defined intraday or end-of-day SLA|Forward completion reversal or correcting entry approved under dual control|Provider and internal manifests match or every difference has closed evidence
RECON|RC05|Portfolio and search projections|Orders executions and ledger are authority; projection is derived|Projection build ID source manifest alias version and per-key version|UTC [startInclusive,endExclusive); adjacent windows share endpoint; projection as-of maps to source UTC interval|Position quantity and cost minor units; indexed document count; freshness age in seconds|Projection totals and keys versus authoritative source window|Projection watermark reaches source exclusive end and no unresolved gap|Projection owner; 5 min portfolio and 30 min search freshness assumptions|Isolated rebuild and conditional cutover; no authoritative correction from projection|Blue-green validation totals match and rollback target retained
RECON|RC06|Notifications|Business authority plus durable notification intent and provider receipt|Intent IDs template version expiry channel and authority version|UTC [startInclusive,endExclusive); adjacent windows share endpoint; provider receipt local time maps to UTC|Intent count delivery receipt count failure count and age in seconds|Required intents versus channel receipts policy exceptions and client inbox|Intent watermark reaches exclusive authority-window end and provider poll complete|Notification owner; mandatory-notice SLA by product and compliance policy|Regenerate only valid intent from authority or record approved exception|Receipt or exception for every required intent; no business mutation

ID	Domain	Authority	Manifest	Window contract	Exact units	Comparison/control totals	Watermark	Break owner/SLA	Repair	Proof
RC01	Accepted orders	Authoritative order command store	Order IDs and terminal-state version	UTC [startInclusive,endExclusive); adjacent windows share endpoint; start included and end excluded	Count of accepted orders and exact ordered quantity in instrument units	Accepted IDs versus execution pending rejected canceled partition	Maximum orderVersion and ingestion timestamp reaches exclusive window end	Order operations; 2 min intraday accepted-without-route SLA	Repair outbox or conditional order state only from command evidence	Every accepted ID has one classified lifecycle state and manifest checksum
RC02	Executions	Execution venue receipts and internal execution authority	Execution IDs venue IDs order IDs and event sequence	UTC [startInclusive,endExclusive); adjacent windows share endpoint; venue local timestamp maps to UTC before comparison	Fill count and exact fill quantity per instrument; exact price in currency minor units with scale	Internal executions versus accepted orders and venue fills	Venue sequence plus internal execution watermark reaches exclusive window end	Trading operations; 1 min duplicate or missing fill SLA	Import missing receipt or mark break; never invent a fill from portfolio	One-to-one venue receipt lineage and no duplicate execution ID
RC03	Ledger balances and reservations	Append-only balanced ledger and reservation authority	Posting-set IDs account IDs currencies effective times and ledger versions	UTC [startInclusive,endExclusive); adjacent windows share endpoint; effective timestamps use governed UTC	Debit and credit minor units by currency; posting count; balance and reservation minor units	Debits equal credits per currency; executions equal postings; available equals balance minus reservations by policy	Ledger sequence and posting effective-time watermark reaches exclusive window end	Ledger operations; zero imbalance tolerance and 5 min reservation mismatch SLA	Conditional reversal or correcting entries with original-posting lineage; never update history	Balanced totals reservation invariant and independent rerun checksum
RC04	Exchange custodian and bank evidence	Signed or controlled provider reports API receipts and statements	Provider file IDs checksums accounts and statement sequence	UTC [startInclusive,endExclusive); adjacent windows share endpoint; provider local business date timezone cutoff calendar retained and deterministic mapping recorded	Exchange fill count and quantity; custodian position quantity; bank cash minor units by currency	Provider totals versus executions ledger cash and settled positions	Provider statement complete marker and internal watermark reaches mapped exclusive end	Trading payments or settlement operations; product-defined intraday or end-of-day SLA	Forward completion reversal or correcting entry approved under dual control	Provider and internal manifests match or every difference has closed evidence
RC05	Portfolio and search projections	Orders executions and ledger are authority; projection is derived	Projection build ID source manifest alias version and per-key version	UTC [startInclusive,endExclusive); adjacent windows share endpoint; projection as-of maps to source UTC interval	Position quantity and cost minor units; indexed document count; freshness age in seconds	Projection totals and keys versus authoritative source window	Projection watermark reaches source exclusive end and no unresolved gap	Projection owner; 5 min portfolio and 30 min search freshness assumptions	Isolated rebuild and conditional cutover; no authoritative correction from projection	Blue-green validation totals match and rollback target retained
RC06	Notifications	Business authority plus durable notification intent and provider receipt	Intent IDs template version expiry channel and authority version	UTC [startInclusive,endExclusive); adjacent windows share endpoint; provider receipt local time maps to UTC	Intent count delivery receipt count failure count and age in seconds	Required intents versus channel receipts policy exceptions and client inbox	Intent watermark reaches exclusive authority-window end and provider poll complete	Notification owner; mandatory-notice SLA by product and compliance policy	Regenerate only valid intent from authority or record approved exception	Receipt or exception for every required intent; no business mutation

Breaks use a conditional lifecycle. Only the current owner can advance a break; all evidence is append-only, and closure requires independent proof.

Model details · task8 breaks

BREAK|OPEN|Control ID manifest difference exact units and first-seen timestamp|Reconciliation service immediately; page domain owner by row SLA|Valid difference exists and is not an approved timing item|Customer state pending investigation; affected scope visible|No mutation|Immutable break ID and source checksums
BREAK|TRIAGED|Classification timing duplicate missing value or external ambiguity plus hypothesis|Domain operations inside SLA; compliance for regulated scope|Evidence identifies authority and affected accounts orders postings|Customer state pending or restricted; support script attached|Approve containment and repair plan under dual control|Triage decision and approver identities
BREAK|CONTAINED|Frozen account product replay lane or outbound action with blast radius|Incident commander and domain owner|No new inconsistent effects enter affected scope|Customer sees explicit delayed restricted or unavailable state|Containment is reversible and does not rewrite authority|Metrics show break count no longer growing
BREAK|CORRECTED|Provider receipt restored event or approved reversal/correcting posting lineage|Authority owner plus independent approver within resolution SLA|Conditional expected-version repair succeeds against unchanged premise|Customer sees corrected or processing state with audit reference|Forward completion reversal or correcting entries only|Old and new versions posting IDs and approvals retained
BREAK|VERIFIED|Fresh reconciliation run independent query and customer-impact review|Reconciliation owner independent of repairer|Original and adjacent windows match exact-unit control totals|Customer state is consistent across authority and projections|No further mutation unless verification opens a new break|Two independent manifests and zero unexplained differences
BREAK|CLOSED|Closure reason root cause linked incident and prevention action|Control owner; compliance sign-off where required|All proof fields complete and SLA disposition recorded|Customer communication delivered or documented unnecessary|Closure is conditional on retained evidence and can reopen|Closed timestamp evidence hashes owner and follow-up ticket

State	Evidence	Owner/SLA	Transition condition	Customer state	Resolution	Proof
OPEN	Control ID manifest difference exact units and first-seen timestamp	Reconciliation service immediately; page domain owner by row SLA	Valid difference exists and is not an approved timing item	Customer state pending investigation; affected scope visible	No mutation	Immutable break ID and source checksums
TRIAGED	Classification timing duplicate missing value or external ambiguity plus hypothesis	Domain operations inside SLA; compliance for regulated scope	Evidence identifies authority and affected accounts orders postings	Customer state pending or restricted; support script attached	Approve containment and repair plan under dual control	Triage decision and approver identities
CONTAINED	Frozen account product replay lane or outbound action with blast radius	Incident commander and domain owner	No new inconsistent effects enter affected scope	Customer sees explicit delayed restricted or unavailable state	Containment is reversible and does not rewrite authority	Metrics show break count no longer growing
CORRECTED	Provider receipt restored event or approved reversal/correcting posting lineage	Authority owner plus independent approver within resolution SLA	Conditional expected-version repair succeeds against unchanged premise	Customer sees corrected or processing state with audit reference	Forward completion reversal or correcting entries only	Old and new versions posting IDs and approvals retained
VERIFIED	Fresh reconciliation run independent query and customer-impact review	Reconciliation owner independent of repairer	Original and adjacent windows match exact-unit control totals	Customer state is consistent across authority and projections	No further mutation unless verification opens a new break	Two independent manifests and zero unexplained differences
CLOSED	Closure reason root cause linked incident and prevention action	Control owner; compliance sign-off where required	All proof fields complete and SLA disposition recorded	Customer communication delivered or documented unnecessary	Closure is conditional on retained evidence and can reopen	Closed timestamp evidence hashes owner and follow-up ticket

Disaster recovery and regional loss

Regional recovery expands the same reasoning to an entire dependency graph. Restore the authority and establish one active writer before resuming unrestricted commands; rebuild projections afterward. Separate the allowed recovery delay and data loss from what the chosen mechanisms and a measured exercise can actually demonstrate.

RTO is maximum acceptable restoration delay; RPO is maximum acceptable data loss measured as time since the last recoverable point. Each row separates the business objective from the selected mechanism and the result measured in a game day; an objective remains unproven until that result exists. Both are set from business impact and tested, not inherited from a service name (C105; AWS DR objectives, A119, retrieved 2026-08-22). The values below are business assumptions, not AWS service promises.

Recover in dependency order: identity/configuration/KMS and network; fenced command authority; ledger/reservations; outbox/log recovery inputs; external exchange/bank/custodian connectivity; projections/search; notifications. Restore and export boundaries remain those of C88/A106. MREC replication is asynchronous, so neither MREC nor PITR proves a zero RPO. MRSC can provide strongly consistent item operations, but Global Tables MRSC does not support DynamoDB transaction APIs: it is therefore incompatible with Task 6's multi-item transactional ledger-posting design unless that design is replaced by a different synchronously durable journal and its serialization and availability tradeoff is accepted. This design retains that transaction model and declares a nonzero business RPO objective that remains unproven until a game day measures actual replica lag and missing IDs. MREC has no replication- latency SLA. Provider effects remain outside either replica guarantee (C89; A107, retrieved 2026-08-22).

Route 53 health checks and ARC recovery controls are pre-provisioned data-plane mechanisms. Failover timing must include DNS TTL, recursive and endpoint caches, existing keepalive connections, SDK connection-pool re-resolution, and client retry identity. A stale client can still reach the old Region, so the old endpoint must return a fenced response rather than accept a command. Failback is a separately approved migration with the same fencing and evidence gates (C106; A120,A121, retrieved 2026-08-22).

Inference: use a single active command/ledger writer epoch and fail closed until the old writer is fenced. Neither MREC nor MRSC removes external-effect ambiguity; failover finishes only after replay, measured recovery-point age and loss meet the RPO objective, reconciliation closes, and stale-client probes pass, while failback repeats the fence (C89,C105,C106; A107,A119,A120,A121, retrieved 2026-08-22).

Model details · task8 dr

DR|DR01|Command and order authority|type=RTO; objective=5 min; service=command_and_order_authority_available|type=RPO; objective=1 min; loss_bound=acknowledged_command_recovery_point_age|MREC command replica plus immutable accepted-command receipts and PITR; no zero-RPO claim|Not yet measured; game day records maximum replica lag and missing accepted-command IDs, so the objective remains unproven|PITR and cross-Region replica plus accepted-command manifest; replay only missing IDs within retained evidence|Identity KMS network then command store then API|One writer epoch in conditional command records; fail closed and old endpoint returns fenced response before promotion|Route 53 and ARC data-plane routing; DNS TTL, endpoint caches, keepalive and re-resolution tested; retry identity survives stale routing; A120 A121 retrieved 2026-08-22|Failover uses stale-endpoint probes before writes; failback is separately fenced, canaried, and approved from manifests|MREC conflict is unacceptable for one command key; MRSC transaction limitation and external effects stop the guarantee|Synthetic lookup and accepted-order manifest reconcile one active epoch; game-day measured recovery point age is at or below the RPO objective
DR|DR02|Ledger and reservations|type=RTO; objective=5 min; service=ledger_and_reservations_available|type=RPO; objective=1 min; loss_bound=acknowledged_posting_recovery_point_age|MREC posting replica plus immutable posting manifests, PITR exports, and provider statements; no zero-RPO claim|Not yet measured; game day records replica lag, missing posting IDs, debit-credit breaks, and recovery point age, so the objective remains unproven|PITR backups exports and posting manifests survive ledger and audit horizon; never restore balance rows without postings|Command authority then ledger then risk and external adapters|Ledger writer epoch and account expected versions; old endpoint returns fenced response before posting|Route 53 and ARC data-plane routing; DNS TTL, endpoint caches, keepalive and re-resolution tested; retry identity survives stale routing; A120 A121 retrieved 2026-08-22|Failover enables ledger writes only after manifest canary; failback repeats fencing, totals, and provider reconciliation|No concurrent regional ledger writers; MRSC cannot preserve the Task 6 multi-item transaction and providers remain external|Debits equal credits by currency; balances reservations executions and provider evidence reconcile; game-day recovery point age is at or below objective
DR|DR03|Outbox and durable logs|type=RTO; objective=15 min; service=outbox_and_durable_log_recovery_available|type=RPO; objective=5 min; loss_bound=outbox_and_log_recovery_point_age|MREC semantic outbox plus retained Kinesis or S3 audit copy and publisher receipts|Not yet measured; game day records oldest missing event, recoverable watermark, replay duplicates, and drain duration, so the objective remains unproven|Retention exceeds detection restore replay and drain; Streams alone is 24 h and archive replay can re-match rules|Authority and ledger before publisher and consumers|Publisher epoch and original event IDs; old Region credentials revoked and writes conditionally fenced|Route 53 and ARC data-plane routing; DNS TTL, endpoint caches, keepalive and re-resolution tested; retry identity survives stale routing; A120 A121 retrieved 2026-08-22|Failover replays only manifest gaps after consumer gate; failback checkpoints replay and revalidates downstream receipts|Replay can duplicate and reorder across sources; retained logs do not make external effects atomic|Accepted authority IDs equal delivered inbox, target receipt, or explicit open break; game-day recovery point age is at or below objective
DR|DR04|Portfolio and search projections|type=RTO; objective=24 h; service=validated_projection_rebuild_and_cutover|type=RPO; inherits=DR01+DR02+DR03; independent_authoritative_loss_budget=none; consequence=rebuild_to_recovered_authority_watermarks|Blue-green rebuild from orders executions ledger and versioned S3 manifests|Not yet measured; game day records rebuild duration, source watermark, missing versions, and alias-cutover time, so the RTO objective remains unproven|Durable authority and versioned manifests cover the full rebuild and catch-up boundary; live Streams only catch up and never authorize correction|All authorities and outbox before projector then search alias|Projection build token and conditional alias switch; command writer fencing remains upstream|Route 53 and ARC data-plane routing; DNS TTL, endpoint caches, keepalive and re-resolution tested; retry identity preserves commands; A120 A121 retrieved 2026-08-22|Failover serves stale as-of view until validated cutover; failback rebuilds separately and conditionally switches alias|Derived stores have no independent authoritative loss budget; they inherit recovered authority points and can remain unavailable or stale|Manifest counts quantities exact values and watermark match recovered authority before either cutover
DR|DR05|Notifications|type=RTO; objective=24 h; service=required_notice_delivery_recovery|type=RPO; objective=5 min; loss_bound=durable_notification_intent_recovery_point_age; consequence=regenerate_only_policy_valid_notices_from_recovered_authority|Regenerate valid notification intents from recovered authority and retained durable intent store|Not yet measured; game day records oldest missing durable intent, expired count, duplicate receipts, and delivery completion, so both objectives remain unproven|Intent retention covers the RPO plus restore and investigation margin but remains bounded by consent template version expiry and legal policy; expired one-time notices are not replayed|Authority and projections before channel replay|Channel sender epoch and intent uniqueness; old sender is revoked before new sender starts|Route 53 and ARC data-plane routing; DNS TTL, endpoint caches, keepalive and re-resolution tested; retry identity protects command lookup; A120 A121 retrieved 2026-08-22|Failover canaries valid notices under provider quota; failback fences sender, resumes manifest checkpoint, and validates receipts|Provider delivery remains external; notices missing beyond the intent RPO must be regenerated from recovered authority when policy-valid or recorded as breaks|Receipt or approved exception for each required notice; durable-intent recovery point age is at or below objective; no duplicate business action

ID	Tier	Illustrative objective RTO	Illustrative objective RPO	Selected mechanism	Measured result	Backup/retention/replay boundary	Dependency order	Single-writer fencing	Routing/client behavior	Failover/failback	Conflict/external-effect limit	Proof
DR01	Command and order authority	type=RTO; objective=5 min; service=command_and_order_authority_available	type=RPO; objective=1 min; loss_bound=acknowledged_command_recovery_point_age	MREC command replica plus immutable accepted-command receipts and PITR; no zero-RPO claim	Not yet measured; game day records maximum replica lag and missing accepted-command IDs, so the objective remains unproven	PITR and cross-Region replica plus accepted-command manifest; replay only missing IDs within retained evidence	Identity KMS network then command store then API	One writer epoch in conditional command records; fail closed and old endpoint returns fenced response before promotion	Route 53 and ARC data-plane routing; DNS TTL, endpoint caches, keepalive and re-resolution tested; retry identity survives stale routing; A120 A121 retrieved 2026-08-22	Failover uses stale-endpoint probes before writes; failback is separately fenced, canaried, and approved from manifests	MREC conflict is unacceptable for one command key; MRSC transaction limitation and external effects stop the guarantee	Synthetic lookup and accepted-order manifest reconcile one active epoch; game-day measured recovery point age is at or below the RPO objective
DR02	Ledger and reservations	type=RTO; objective=5 min; service=ledger_and_reservations_available	type=RPO; objective=1 min; loss_bound=acknowledged_posting_recovery_point_age	MREC posting replica plus immutable posting manifests, PITR exports, and provider statements; no zero-RPO claim	Not yet measured; game day records replica lag, missing posting IDs, debit-credit breaks, and recovery point age, so the objective remains unproven	PITR backups exports and posting manifests survive ledger and audit horizon; never restore balance rows without postings	Command authority then ledger then risk and external adapters	Ledger writer epoch and account expected versions; old endpoint returns fenced response before posting	Route 53 and ARC data-plane routing; DNS TTL, endpoint caches, keepalive and re-resolution tested; retry identity survives stale routing; A120 A121 retrieved 2026-08-22	Failover enables ledger writes only after manifest canary; failback repeats fencing, totals, and provider reconciliation	No concurrent regional ledger writers; MRSC cannot preserve the Task 6 multi-item transaction and providers remain external	Debits equal credits by currency; balances reservations executions and provider evidence reconcile; game-day recovery point age is at or below objective
DR03	Outbox and durable logs	type=RTO; objective=15 min; service=outbox_and_durable_log_recovery_available	type=RPO; objective=5 min; loss_bound=outbox_and_log_recovery_point_age	MREC semantic outbox plus retained Kinesis or S3 audit copy and publisher receipts	Not yet measured; game day records oldest missing event, recoverable watermark, replay duplicates, and drain duration, so the objective remains unproven	Retention exceeds detection restore replay and drain; Streams alone is 24 h and archive replay can re-match rules	Authority and ledger before publisher and consumers	Publisher epoch and original event IDs; old Region credentials revoked and writes conditionally fenced	Route 53 and ARC data-plane routing; DNS TTL, endpoint caches, keepalive and re-resolution tested; retry identity survives stale routing; A120 A121 retrieved 2026-08-22	Failover replays only manifest gaps after consumer gate; failback checkpoints replay and revalidates downstream receipts	Replay can duplicate and reorder across sources; retained logs do not make external effects atomic	Accepted authority IDs equal delivered inbox, target receipt, or explicit open break; game-day recovery point age is at or below objective
DR04	Portfolio and search projections	type=RTO; objective=24 h; service=validated_projection_rebuild_and_cutover	type=RPO; inherits=DR01+DR02+DR03; independent_authoritative_loss_budget=none; consequence=rebuild_to_recovered_authority_watermarks	Blue-green rebuild from orders executions ledger and versioned S3 manifests	Not yet measured; game day records rebuild duration, source watermark, missing versions, and alias-cutover time, so the RTO objective remains unproven	Durable authority and versioned manifests cover the full rebuild and catch-up boundary; live Streams only catch up and never authorize correction	All authorities and outbox before projector then search alias	Projection build token and conditional alias switch; command writer fencing remains upstream	Route 53 and ARC data-plane routing; DNS TTL, endpoint caches, keepalive and re-resolution tested; retry identity preserves commands; A120 A121 retrieved 2026-08-22	Failover serves stale as-of view until validated cutover; failback rebuilds separately and conditionally switches alias	Derived stores have no independent authoritative loss budget; they inherit recovered authority points and can remain unavailable or stale	Manifest counts quantities exact values and watermark match recovered authority before either cutover
DR05	Notifications	type=RTO; objective=24 h; service=required_notice_delivery_recovery	type=RPO; objective=5 min; loss_bound=durable_notification_intent_recovery_point_age; consequence=regenerate_only_policy_valid_notices_from_recovered_authority	Regenerate valid notification intents from recovered authority and retained durable intent store	Not yet measured; game day records oldest missing durable intent, expired count, duplicate receipts, and delivery completion, so both objectives remain unproven	Intent retention covers the RPO plus restore and investigation margin but remains bounded by consent template version expiry and legal policy; expired one-time notices are not replayed	Authority and projections before channel replay	Channel sender epoch and intent uniqueness; old sender is revoked before new sender starts	Route 53 and ARC data-plane routing; DNS TTL, endpoint caches, keepalive and re-resolution tested; retry identity protects command lookup; A120 A121 retrieved 2026-08-22	Failover canaries valid notices under provider quota; failback fences sender, resumes manifest checkpoint, and validates receipts	Provider delivery remains external; notices missing beyond the intent RPO must be regenerated from recovered authority when policy-valid or recorded as breaks	Receipt or approved exception for each required notice; durable-intent recovery point age is at or below objective; no duplicate business action

Quarterly game days restore backups to a new environment, promote a fenced writer, replay outbox/logs at the planned split, reconcile every exact-unit control, and verify customer states. At least annually, exercise full Region failover and failback. Abort on a second writer, growing ledger break, missing encryption/config dependency, or live-traffic SLO breach. Retain timelines, commands, manifests, approvals, and proof against the RTO/RPO clock (F14,F15; A106,A119-A121, retrieved 2026-08-22).

Operator runbooks

Thresholds below are illustrative planning inputs. Replace them only through an owned SLO/capacity review. Each runbook embodies detect, contain, bounded action, and repair; no runbook declares success from queue depth alone (C43,C45,C48,C68; F03,F13,F14).

Model details · task8 runbooks

RUNBOOK|RBK01|Ambiguous order response|Client timeout plus command IN_PROGRESS older than 2 s or accepted-without-response count above zero|Stop duplicate logical command; return pending and lookup token|Query fingerprint order ID order version and outbox; preserve request correlation|One client retry inside 8 s then lookup every 1 s for 5 s|restore=retry_policy_version; checkpoint=command_manifest+lookup_cursor; release=one_fingerprint_one_order_one_result_proven; irreversible=escalate_customer_or_ledger_mutation_to_order_incident_lead|Any mismatched fingerprint or two order IDs|Order API on-call; incident lead if unresolved 2 min|Pending not failed and not safely resubmittable|Reconcile command order outbox and return durable result|One fingerprint one order ID one final customer result and no open break
RUNBOOK|RBK02|Producer partial or unknown result|FailedEntryCount above zero missing response entry or outbox age above 30 s|Stop whole-batch retry; persist attempted manifest and isolate unknowns|Inspect each entry event ID error bus rule receipt and downstream inbox|Retry explicit failures maximum 5 over 2 min at publisher cap; lookup unknowns|restore=publisher_cap+retry_policy_version; checkpoint=attempted_manifest+per_entry_result_cursor; release=all_unknown_entries_resolved; irreversible=escalate_republish_or_external_effect_to_messaging_and_order_owners|Unknown count grows or downstream age exceeds 60 s|Messaging owner; order owner for accepted commands|Accepted-pending until downstream proof|Compare attempted explicit success explicit failure and resolved unknown; replay original IDs|Manifest balances and downstream receipt or open break exists for every entry
RUNBOOK|RBK03|Kinesis or queue backlog|Iterator or oldest age above 60 s for 5 min or modeled retention margin below 2 h|Pause replay; shed optional work; cap concurrency to protect ledger and live traffic|Measure lambda mu skew throttles poison keys dependency latency and per-class wait|Replay at maximum 25 percent measured commit capacity; target 200 records/s in example|restore=concurrency+admission_policy_version; checkpoint=replay_manifest+last_committed_source_position; release=live_age_below_30s_for_15m_and_net_drain_positive; irreversible=escalate_expiry_or_dropped_obligation_to_incident_commander|Live p99 breaches SLO net drain non-positive or any reconciliation break grows|Incident commander consumer owner and dependency owner|Orders show delayed with watermark; authority remains available if safe|Drain under B divided by net rate; validate checkpoints gaps inbox and control totals|Age below 30 s for 15 min no starvation and all admitted work reconciled
RUNBOOK|RBK04|Poison item|Same event fails twice or non-retryable schema validation occurs once|Quarantine full payload; isolate key or group; preserve ordered lane evidence|Record schema version producer hash error source sequence and downstream compatibility|Zero ordinary retries for non-retryable; offline dry run then one-key or 1 percent canary|restore=consumer_version+event_source_configuration; checkpoint=quarantine_manifest+last_safe_sequence; release=canary_effect_and_gap_reconciliation_pass; irreversible=escalate_transform_or_side_effect_to_schema_and_domain_owners|Canary error any unintended side effect or live age growth|Schema and consumer owners; domain owner for correction approval|Affected item pending; unrelated keys continue where order permits|Governed transform with new lineage or consumer fix; replay original identity and reconcile|Canary and batch pass; gap closes; counts versions and effects match
RUNBOOK|RBK05|Projection gap|Expected version n but receives above n or watermark lag exceeds 5 min|Park gap; keep old view with as-of time; block cutover and suppress side effects|Query authority versions manifest checkpoint inbox and target build ID|Fetch narrow missing range; otherwise blue-green backfill capped at 25 percent|restore=old_alias+projector_version; checkpoint=old_and_new_build_manifests+replay_watermark; release=no_gaps_and_control_totals_match_authority; irreversible=escalate_index_deletion_or_authority_correction_to_projection_and_domain_owners|Authority mismatch unexplained duplicate version or live SLO impact|Projection owner; domain owner approves source totals|Stale view clearly labeled; never used for authorization|Catch up isolated target compare quantities values counts then conditional alias switch|No gaps; watermark equals target; two manifests match and rollback target retained
RUNBOOK|RBK06|External exchange or bank timeout|Call timed out and no receipt after 1 s or callback age exceeds product threshold|Do not repeat effect; open circuit for optional requests; preserve intent and block conflict|Use provider request ID status API callback log statement and internal ledger intent|Five status lookups with full jitter over 5 min; no blind effect retry|restore=circuit+timeout_policy_version_after_provider_ready; checkpoint=intent_manifest+last_provider_receipt_cursor; release=provider_receipt_intent_and_ledger_agree; irreversible=escalate_provider_cancel_reversal_or_posting_to_operations_and_dual_control|Provider reports conflicting states or lookup budget expires|Trading or payments operations; compliance by product SLA|Pending-external and not failed; support cannot resubmit|Match provider evidence then forward-complete reverse or correct under dual control|Provider receipt intent and ledger agree; customer state updated; break independently closed
RUNBOOK|RBK07|Ledger or reconciliation break|Any debit-credit imbalance duplicate fill missing posting or reservation mismatch; zero tolerance|Freeze affected account or product writes; preserve statements and manifests|Recompute exact units by currency and instrument; trace orders executions postings reservations provider evidence|No automated retry of money mutation; bounded evidence queries then conditional approved correction|restore=query+capacity_policy_only; checkpoint=original_and_adjacent_manifests+repair_version; release=independent_reconciliation_verified; irreversible=escalate_reversal_or_correcting_entry_to_dual_control|Break scope expands authority is uncertain or evidence checksum differs|Ledger operations incident commander compliance and independent approver|Restricted or pending with explicit support state|Use reversal or correcting entries with lineage; rerun original and adjacent windows|Balanced totals and reservations; provider match; two-person VERIFIED then CLOSED
RUNBOOK|RBK08|Region failover|Regional business probe fails 2 min and incident commander declares disaster|Stop writes; revoke old writer credentials or epoch; do not shift command traffic yet|Verify replication lag backups KMS config network external connectivity accepted-command manifest; inspect Route 53 and ARC data-plane state DNS TTL endpoint caches keepalive re-resolution retry identity and fenced old-Region responses; A120 A121 retrieved 2026-08-22|Recover authority-first; canary reads then writes; replay within 25 percent capacity split|restore=last_fenced_routing+capacity_configuration; checkpoint=failover_manifest+writer_epoch+replay_watermark; release=stale_client_probes_and_financial_control_totals_pass; irreversible=escalate_promotion_data_correction_or_failback_to_incident_commander|Second writer detected ledger break grows RPO evidence missing or stale endpoint accepts a write|Incident commander platform command ledger external and compliance owners|Unavailable for commands until fenced; projections may show stale as-of state|Promote one epoch restore missing data replay outbox rebuild projections reconcile externals; separately fence and approve failback|One writer; measured restoration duration and recovery-point age/loss meet RTO/RPO objectives; DNS and keepalive stale-client probes pass; control totals clean; failback game day approved

ID	Scenario	Entry signal/threshold	Immediate safety action	Diagnosis/evidence	Bounded action/rate	Rollback/resume	Abort condition	Owner/escalation	Customer state	Reconciliation/proof	Exit criteria
RBK01	Ambiguous order response	Client timeout plus command IN_PROGRESS older than 2 s or accepted-without-response count above zero	Stop duplicate logical command; return pending and lookup token	Query fingerprint order ID order version and outbox; preserve request correlation	One client retry inside 8 s then lookup every 1 s for 5 s	restore=retry_policy_version; checkpoint=command_manifest+lookup_cursor; release=one_fingerprint_one_order_one_result_proven; irreversible=escalate_customer_or_ledger_mutation_to_order_incident_lead	Any mismatched fingerprint or two order IDs	Order API on-call; incident lead if unresolved 2 min	Pending not failed and not safely resubmittable	Reconcile command order outbox and return durable result	One fingerprint one order ID one final customer result and no open break
RBK02	Producer partial or unknown result	FailedEntryCount above zero missing response entry or outbox age above 30 s	Stop whole-batch retry; persist attempted manifest and isolate unknowns	Inspect each entry event ID error bus rule receipt and downstream inbox	Retry explicit failures maximum 5 over 2 min at publisher cap; lookup unknowns	restore=publisher_cap+retry_policy_version; checkpoint=attempted_manifest+per_entry_result_cursor; release=all_unknown_entries_resolved; irreversible=escalate_republish_or_external_effect_to_messaging_and_order_owners	Unknown count grows or downstream age exceeds 60 s	Messaging owner; order owner for accepted commands	Accepted-pending until downstream proof	Compare attempted explicit success explicit failure and resolved unknown; replay original IDs	Manifest balances and downstream receipt or open break exists for every entry
RBK03	Kinesis or queue backlog	Iterator or oldest age above 60 s for 5 min or modeled retention margin below 2 h	Pause replay; shed optional work; cap concurrency to protect ledger and live traffic	Measure lambda mu skew throttles poison keys dependency latency and per-class wait	Replay at maximum 25 percent measured commit capacity; target 200 records/s in example	restore=concurrency+admission_policy_version; checkpoint=replay_manifest+last_committed_source_position; release=live_age_below_30s_for_15m_and_net_drain_positive; irreversible=escalate_expiry_or_dropped_obligation_to_incident_commander	Live p99 breaches SLO net drain non-positive or any reconciliation break grows	Incident commander consumer owner and dependency owner	Orders show delayed with watermark; authority remains available if safe	Drain under B divided by net rate; validate checkpoints gaps inbox and control totals	Age below 30 s for 15 min no starvation and all admitted work reconciled
RBK04	Poison item	Same event fails twice or non-retryable schema validation occurs once	Quarantine full payload; isolate key or group; preserve ordered lane evidence	Record schema version producer hash error source sequence and downstream compatibility	Zero ordinary retries for non-retryable; offline dry run then one-key or 1 percent canary	restore=consumer_version+event_source_configuration; checkpoint=quarantine_manifest+last_safe_sequence; release=canary_effect_and_gap_reconciliation_pass; irreversible=escalate_transform_or_side_effect_to_schema_and_domain_owners	Canary error any unintended side effect or live age growth	Schema and consumer owners; domain owner for correction approval	Affected item pending; unrelated keys continue where order permits	Governed transform with new lineage or consumer fix; replay original identity and reconcile	Canary and batch pass; gap closes; counts versions and effects match
RBK05	Projection gap	Expected version n but receives above n or watermark lag exceeds 5 min	Park gap; keep old view with as-of time; block cutover and suppress side effects	Query authority versions manifest checkpoint inbox and target build ID	Fetch narrow missing range; otherwise blue-green backfill capped at 25 percent	restore=old_alias+projector_version; checkpoint=old_and_new_build_manifests+replay_watermark; release=no_gaps_and_control_totals_match_authority; irreversible=escalate_index_deletion_or_authority_correction_to_projection_and_domain_owners	Authority mismatch unexplained duplicate version or live SLO impact	Projection owner; domain owner approves source totals	Stale view clearly labeled; never used for authorization	Catch up isolated target compare quantities values counts then conditional alias switch	No gaps; watermark equals target; two manifests match and rollback target retained
RBK06	External exchange or bank timeout	Call timed out and no receipt after 1 s or callback age exceeds product threshold	Do not repeat effect; open circuit for optional requests; preserve intent and block conflict	Use provider request ID status API callback log statement and internal ledger intent	Five status lookups with full jitter over 5 min; no blind effect retry	restore=circuit+timeout_policy_version_after_provider_ready; checkpoint=intent_manifest+last_provider_receipt_cursor; release=provider_receipt_intent_and_ledger_agree; irreversible=escalate_provider_cancel_reversal_or_posting_to_operations_and_dual_control	Provider reports conflicting states or lookup budget expires	Trading or payments operations; compliance by product SLA	Pending-external and not failed; support cannot resubmit	Match provider evidence then forward-complete reverse or correct under dual control	Provider receipt intent and ledger agree; customer state updated; break independently closed
RBK07	Ledger or reconciliation break	Any debit-credit imbalance duplicate fill missing posting or reservation mismatch; zero tolerance	Freeze affected account or product writes; preserve statements and manifests	Recompute exact units by currency and instrument; trace orders executions postings reservations provider evidence	No automated retry of money mutation; bounded evidence queries then conditional approved correction	restore=query+capacity_policy_only; checkpoint=original_and_adjacent_manifests+repair_version; release=independent_reconciliation_verified; irreversible=escalate_reversal_or_correcting_entry_to_dual_control	Break scope expands authority is uncertain or evidence checksum differs	Ledger operations incident commander compliance and independent approver	Restricted or pending with explicit support state	Use reversal or correcting entries with lineage; rerun original and adjacent windows	Balanced totals and reservations; provider match; two-person VERIFIED then CLOSED
RBK08	Region failover	Regional business probe fails 2 min and incident commander declares disaster	Stop writes; revoke old writer credentials or epoch; do not shift command traffic yet	Verify replication lag backups KMS config network external connectivity accepted-command manifest; inspect Route 53 and ARC data-plane state DNS TTL endpoint caches keepalive re-resolution retry identity and fenced old-Region responses; A120 A121 retrieved 2026-08-22	Recover authority-first; canary reads then writes; replay within 25 percent capacity split	restore=last_fenced_routing+capacity_configuration; checkpoint=failover_manifest+writer_epoch+replay_watermark; release=stale_client_probes_and_financial_control_totals_pass; irreversible=escalate_promotion_data_correction_or_failback_to_incident_commander	Second writer detected ledger break grows RPO evidence missing or stale endpoint accepts a write	Incident commander platform command ledger external and compliance owners	Unavailable for commands until fenced; projections may show stale as-of state	Promote one epoch restore missing data replay outbox rebuild projections reconcile externals; separately fence and approve failback	One writer; measured restoration duration and recovery-point age/loss meet RTO/RPO objectives; DNS and keepalive stale-client probes pass; control totals clean; failback game day approved

Senior interview contract

Each major topic must be defended as an operating decision, not a vocabulary definition. The source routes below deliberately reuse C43-C48,C61 and the named conceptual anchors F01-F03,F08,F11-F14.

Model details · task8 topics

TOPIC|TP01|Failure surface|Expose ambiguity before choosing mechanisms|Fits multi-boundary financial workflows; poor fit only for a truly atomic local operation|Proof stops at each producer transport consumer store and external-effect boundary|Order acceptance through execution ledger projection and notification|Prevent detect contain repair each row; unresolved state remains explicit|Variable evidence storage and checks; fixed failure taxonomy ownership and drills|Unknown age per boundary accepted-without-effect and reconciliation breaks|I trace authority ambiguity budget owner and proof before naming AWS controls|Ambiguous order publication from CS01-CS03|A green dashboard or DLQ checkbox proves recovery|C43 C45 C48 F03 F11 F12 F14
TOPIC|TP02|Idempotency layers|Prevent retry from multiplying one logical effect|Fits repeatable commands and consumers; poor fit as a substitute for domain uniqueness|Transport handler command and ledger identities stop at different transactions|Client order ID event ID command fingerprint and posting set|Lookup mismatches expired leases and ambiguous effects require repair|Variable idempotency reads writes retention; fixed key governance and support policy|Duplicate-hit mismatch stale-IN_PROGRESS and repeated-posting counters|One ID never proves all layers; I name key state transaction expiry and effect|Order retry plus projector duplicate plus ledger posting|FIFO or acknowledgement means one business effect|C40 C47 C90 F02 F08 F11
TOPIC|TP03|Retry and timeout|Recover transient faults without storms or duplicate effects|Fits classified transient failures; poor fit for validation conflicts and ambiguous money movement|Deadline timeout owner maximum attempts and age stop at lookup or reconciliation|Producer rejection handler timeout and provider status lookup|Full jitter one owned layer and explicit pre-invocation versus invoked-handler paths|Variable extra attempts latency and capacity; fixed policy testing and incident ownership|Attempts by class deadline exhaustion oldest age and ambiguous queue|I retry only safe transient work; ambiguity changes the operation to lookup|Exchange timeout after possible fill|Retry until success or retry at every layer|C45 C65 C76 F03 F11 F12 A26 A98
TOPIC|TP04|Overload containment|Protect authority and fairness when demand exceeds safe commit rate|Fits burst dependency slowdown and replay; poor fit as a correction for wrong data|Bulkhead cap breaker shedding admission queue and fairness each stop at load not correctness|Live commands share DynamoDB and Lambda with projection and replay|Shed optional work cap replay reserve authority and reconcile expired obligations|Variable rejected deferred and idle reserve capacity; fixed SLO policy and capacity tests|Lambda throttle oldest age wait and rejection by tenant key priority|Autoscaling may add supply; admission and bounded debt decide safety|Reserve ledger lane while throttling search rebuild|Conflating autoscaling with backpressure or circuit breaking with correctness|C44 C61 C104 F03 F13 F14 A117
TOPIC|TP05|Quarantine and replay|Preserve failed evidence and reprocess only after readiness|Fits retained replayable inputs; poor fit after payload expiry or irreversible effect|Each EventBridge target DLQ archive SQS Lambda Kinesis Streams SNS and Firehose boundary has distinct payload route and order|Poison projection event and failed notification|Permissions retention canary rate idempotency delete acknowledgement and post-validation govern replay|Variable retained bytes and replay work; fixed tooling permissions and game days|Failure destination success age replay rate and business control totals|A target DLQ holds one target failure; archive replay can re-match source-bus rules; neither alone proves repair|Kinesis failed invocation retained in S3 and replayed through isolated lane|All failures go to the DLQ then redrive at full speed|C43 C57 C62 C63 C64 C66 C76 C103 A81 A84 A86 A98 A118
TOPIC|TP06|Ordering repair|Preserve per-invariant causality under duplicates concurrency and backfill|Fits versioned aggregates; poor fit for fabricated global arrival order|Source version single writer expected-version apply and gap policy stop at named scope|Order aggregate ledger posting set and portfolio key|Buffer gaps reject stale isolate replay and reconcile deterministic merge|Variable serialization wait and buffers; fixed sequence ownership conflict tooling|Gap age stale duplicate conflict rate and watermark|I pay serialization only where an invariant needs it and reconcile wider views|Account-instrument portfolio versions from execution authority|FIFO removes idempotency or optimistic lock deduplicates events|C34 C40 C41 C72 C74 C84 C93 F01 F02
TOPIC|TP07|Financial reconciliation|Detect and repair silent divergence using independent authoritative evidence|Fits money quantity and regulated notices; poor fit when a projection is treated as authority|Manifest window watermark exact units dual control and proof of closure|Orders executions postings reservations provider statements and projections|Break lifecycle contains then forward-completes reverses or corrects conditionally|Variable comparison queries evidence retention and manual cases; fixed control ownership and SLA|Imbalance missing posting duplicate fill reservation mismatch and break age|Availability is not correctness; every accepted obligation must reconcile to authority|Bank minor-unit statement versus cash ledger and reservations|Derived portfolio authorizes a money correction|C46 C47 C48 C91 F08 F14 F15 F16 F17
TOPIC|TP08|Disaster recovery|Restore one correct system rather than two conflicting writers|Fits Region loss and corruption recovery; poor fit as an untested multi-Region badge|Business RTO/RPO objectives selected mechanisms measured restoration duration and recovery-point age/loss backup replay fence routing external effects and reconciliation stop at declared tier|Command ledger outbox projections and notifications recover in dependency order|Fence old writer route through Route 53 and ARC data plane probe stale clients restore canary replay reconcile failover and separately failback|Variable replica backup replay and idle capacity; fixed IaC runbooks and game days|Restoration clock recovery-point age/loss replication lag DNS TTL caches connections writer epoch and control totals|Multi-Region shortens some recovery paths but never proves zero loss or globally atomic effects|Ledger Region failover reconciled with exchange custodian and bank|Treating MREC or PITR objectives as measured lossless recovery or assuming Route 53 instantly removes old clients|C88 C89 C105 C106 A106 A107 A119 A120 A121 F14 F15

ID	Topic	Why	Fit/poor fit	Guarantee/stopping boundary	Workload	Failure/recovery	Variable/fixed burden	Actionable metrics	Concise defense	Fintech example	Anti-pattern	Sources
TP01	Failure surface	Expose ambiguity before choosing mechanisms	Fits multi-boundary financial workflows; poor fit only for a truly atomic local operation	Proof stops at each producer transport consumer store and external-effect boundary	Order acceptance through execution ledger projection and notification	Prevent detect contain repair each row; unresolved state remains explicit	Variable evidence storage and checks; fixed failure taxonomy ownership and drills	Unknown age per boundary accepted-without-effect and reconciliation breaks	I trace authority ambiguity budget owner and proof before naming AWS controls	Ambiguous order publication from CS01-CS03	A green dashboard or DLQ checkbox proves recovery	C43 C45 C48 F03 F11 F12 F14
TP02	Idempotency layers	Prevent retry from multiplying one logical effect	Fits repeatable commands and consumers; poor fit as a substitute for domain uniqueness	Transport handler command and ledger identities stop at different transactions	Client order ID event ID command fingerprint and posting set	Lookup mismatches expired leases and ambiguous effects require repair	Variable idempotency reads writes retention; fixed key governance and support policy	Duplicate-hit mismatch stale-IN_PROGRESS and repeated-posting counters	One ID never proves all layers; I name key state transaction expiry and effect	Order retry plus projector duplicate plus ledger posting	FIFO or acknowledgement means one business effect	C40 C47 C90 F02 F08 F11
TP03	Retry and timeout	Recover transient faults without storms or duplicate effects	Fits classified transient failures; poor fit for validation conflicts and ambiguous money movement	Deadline timeout owner maximum attempts and age stop at lookup or reconciliation	Producer rejection handler timeout and provider status lookup	Full jitter one owned layer and explicit pre-invocation versus invoked-handler paths	Variable extra attempts latency and capacity; fixed policy testing and incident ownership	Attempts by class deadline exhaustion oldest age and ambiguous queue	I retry only safe transient work; ambiguity changes the operation to lookup	Exchange timeout after possible fill	Retry until success or retry at every layer	C45 C65 C76 F03 F11 F12 A26 A98
TP04	Overload containment	Protect authority and fairness when demand exceeds safe commit rate	Fits burst dependency slowdown and replay; poor fit as a correction for wrong data	Bulkhead cap breaker shedding admission queue and fairness each stop at load not correctness	Live commands share DynamoDB and Lambda with projection and replay	Shed optional work cap replay reserve authority and reconcile expired obligations	Variable rejected deferred and idle reserve capacity; fixed SLO policy and capacity tests	Lambda throttle oldest age wait and rejection by tenant key priority	Autoscaling may add supply; admission and bounded debt decide safety	Reserve ledger lane while throttling search rebuild	Conflating autoscaling with backpressure or circuit breaking with correctness	C44 C61 C104 F03 F13 F14 A117
TP05	Quarantine and replay	Preserve failed evidence and reprocess only after readiness	Fits retained replayable inputs; poor fit after payload expiry or irreversible effect	Each EventBridge target DLQ archive SQS Lambda Kinesis Streams SNS and Firehose boundary has distinct payload route and order	Poison projection event and failed notification	Permissions retention canary rate idempotency delete acknowledgement and post-validation govern replay	Variable retained bytes and replay work; fixed tooling permissions and game days	Failure destination success age replay rate and business control totals	A target DLQ holds one target failure; archive replay can re-match source-bus rules; neither alone proves repair	Kinesis failed invocation retained in S3 and replayed through isolated lane	All failures go to the DLQ then redrive at full speed	C43 C57 C62 C63 C64 C66 C76 C103 A81 A84 A86 A98 A118
TP06	Ordering repair	Preserve per-invariant causality under duplicates concurrency and backfill	Fits versioned aggregates; poor fit for fabricated global arrival order	Source version single writer expected-version apply and gap policy stop at named scope	Order aggregate ledger posting set and portfolio key	Buffer gaps reject stale isolate replay and reconcile deterministic merge	Variable serialization wait and buffers; fixed sequence ownership conflict tooling	Gap age stale duplicate conflict rate and watermark	I pay serialization only where an invariant needs it and reconcile wider views	Account-instrument portfolio versions from execution authority	FIFO removes idempotency or optimistic lock deduplicates events	C34 C40 C41 C72 C74 C84 C93 F01 F02
TP07	Financial reconciliation	Detect and repair silent divergence using independent authoritative evidence	Fits money quantity and regulated notices; poor fit when a projection is treated as authority	Manifest window watermark exact units dual control and proof of closure	Orders executions postings reservations provider statements and projections	Break lifecycle contains then forward-completes reverses or corrects conditionally	Variable comparison queries evidence retention and manual cases; fixed control ownership and SLA	Imbalance missing posting duplicate fill reservation mismatch and break age	Availability is not correctness; every accepted obligation must reconcile to authority	Bank minor-unit statement versus cash ledger and reservations	Derived portfolio authorizes a money correction	C46 C47 C48 C91 F08 F14 F15 F16 F17
TP08	Disaster recovery	Restore one correct system rather than two conflicting writers	Fits Region loss and corruption recovery; poor fit as an untested multi-Region badge	Business RTO/RPO objectives selected mechanisms measured restoration duration and recovery-point age/loss backup replay fence routing external effects and reconciliation stop at declared tier	Command ledger outbox projections and notifications recover in dependency order	Fence old writer route through Route 53 and ARC data plane probe stale clients restore canary replay reconcile failover and separately failback	Variable replica backup replay and idle capacity; fixed IaC runbooks and game days	Restoration clock recovery-point age/loss replication lag DNS TTL caches connections writer epoch and control totals	Multi-Region shortens some recovery paths but never proves zero loss or globally atomic effects	Ledger Region failover reconciled with exchange custodian and bank	Treating MREC or PITR objectives as measured lossless recovery or assuming Route 53 instantly removes old clients	C88 C89 C105 C106 A106 A107 A119 A120 A121 F14 F15

Sources used in this chapter

Stable concepts: Kleppmann and Riccomini (F01), Enterprise Integration Patterns (F02), Nygard, Release It! (F03), Fowler accounting patterns (F08), Featonby on idempotent APIs (F11), Brooker on timeouts/retries/jitter (F12), Yanacek on queue backlogs (F13), Google SRE (F14), SRE Workbook (F15), SLO chapter (F16), and the FIXimate FIX.Latest top-level specification (F18, retrieved 2026-08-24) with Harris's trading-domain anchor (F17).

Current AWS behavior, all retrieved 2026-08-22: Lambda with SQS (A02), Lambda with Kinesis (A03), Step Functions error handling (A26), CloudWatch (A36), EventBridge target DLQs (A81), EventBridge archive/replay (A84), SQS visibility (A85), SNS subscription DLQs (A86), Lambda/Kinesis parameters and failures (A98), DynamoDB backup/export (A106), DynamoDB Global Tables (A107), Lambda SQS scaling (A117), SQS redrive (A118), AWS Well-Architected DR (A119), Route 53 DNS failover best practices (A120), and ARC routing-control best practices (A121).

Takeaway and next step

A recovery procedure is complete only when it names evidence, an owner, a stopping condition, and independent business validation. Check that you can explain why ambiguity changes retry into lookup, why no spare capacity means no safe replay, and why a regional switch needs writer fencing. Next, apply these controls to Fintech and trading architecture.