Preserve command identity across a regional routing retry
A gateway retries an update in another region after losing the response, potentially applying the shipment change twice.
- Focused work estimate
- 4h + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- Idempotency · Distributed failure
Estimated field mix
- Distributed systems50%
- System design30%
- Backend20%
Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence.
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Project context
A fictional logistics dashboard serves distant customers from one primary region. Stakeholders want faster reads and outage recovery but have not agreed which data may be stale.
Setup prerequisites
- Create a local primary/replica simulator and synthetic shipment records.
- Use local models; no multi-region infrastructure is provisioned.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
- AREGION-101 · Classify shipment reads by tolerated staleness
- AREGION-102 · Calculate regional latency contributions with stated assumptions
- AREGION-103 · Record the decision between regional caching and replica reads
- AREGION-104 · Define a read-after-write token for shipment changes
- AREGION-105 · Fence regional write authority before promoting a standby
Acceptance criteria
- Use a stable command key across routing attempts.
- Bind the key to target, actor and canonical input.
- Return unknown until committed status can be resolved safely.
Implementation constraints
- Do not infer an absent commit from a connection timeout.
Verification to include
- Lose the response after commit and resolve one logical change.
- Change input under the same key and return conflict.
Deliverables
- Cross-route command contract and timeout probe
Rollout and recovery
Use the contract in the local gateway prototype; suspend retries if deduplication authority is unavailable.
Value of the work
For the engineer: Practice consistency tradeoffs, failover authority and recovery assumptions.
For the team: Review regional availability proposals with explicit data-loss and staleness limits.
Evidence boundaries
Outcome Evidence: Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs.
Ownership Evidence: Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence.