Record authoritative product revision with each cached projection
An API instance receives two cached values but cannot tell which reflects the newer database update.
- Focused work estimate
- 1h 30m + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- Versioning · Cache contracts
Estimated field mix
- Distributed systems80%
- API design20%
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 wholesale portal caches product availability descriptions across several API instances. Delayed invalidations and slow refreshes bring back old content after edits.
Setup prerequisites
- Create two local cache clients and a synthetic authoritative product store.
- Use a fake clock and controllable read/write barriers.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- Store source revision and projection version with the value.
- Reject malformed or unknown envelopes.
- Keep fetch time separate from source revision.
Implementation constraints
- Do not use cache write time as data ordering authority.
Verification to include
- Compare cached revisions 7 and 8.
- Read an envelope missing revision and treat it as unusable.
Deliverables
- Versioned cache envelope
Rollout and recovery
Deploy readers that accept the envelope before enabling new writers; miss safely on legacy values.
Value of the work
For the engineer: Practice cache consistency, version guards and recoverable invalidation.
For the team: Review fast derived reads without losing authoritative state or tenant isolation.
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.