Advance the feed checkpoint only with the projected transaction
The consumer acknowledges a change before updating the read model; a crash permanently loses the disabled preference.
- Focused work estimate
- 3h 30m + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Transactions · Idempotency
Estimated field mix
- Database engineering50%
- Data engineering50%
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 messaging service builds a read model from database changes. Restarts and schema changes can re-enable preferences that customers disabled.
Setup prerequisites
- Create synthetic preference records and a replayable local change log.
- Use adapters or fixtures without provisioning a production broker.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- Apply projection and checkpoint in one durable transaction.
- Duplicate delivery is a no-op at the same position.
- Failed application leaves the previous checkpoint intact.
Implementation constraints
- Scope checkpoints to source partition and consumer generation.
Verification to include
- Replay a committed change and keep one result.
- Fail between modeled projection and checkpoint writes and retry successfully.
Deliverables
- Transactional consumer and interruption test
Rollout and recovery
Canary one synthetic partition; stop consumption on checkpoint divergence.
Value of the work
For the engineer: Practice change-feed ordering, snapshots and privacy-preserving deletion.
For the team: Review whether replicated customer preferences remain correct during recovery.
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.