Keep archive cache misses distinct from provider failures
Any cache read error is treated as a miss and hides damaged storage. Define typed outcomes.
- Focused work estimate
- 1h + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- Error modeling · Storage
Estimated field mix
- Storage systems70%
- Site reliability30%
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
Fictional media archive Ash serves generated byte fixtures through a fast local cache and slower provider stub. Both tiers run locally.
Setup prerequisites
- Create immutable generated blobs with known digests.
- Implement controllable cache and origin adapters with read failures.
Preceding work
No earlier ticket is required. Complete the project setup above.
Acceptance criteria
- Missing key is a miss
- Permission failure is operational error
- Origin reads follow documented fallback policy
Implementation constraints
- Do not swallow arbitrary filesystem exceptions.
Verification to include
- Read absent fixture
- Inject permission failure
Deliverables
- Cache result contract
Rollout and recovery
Bypass cache on operational failure while reporting it.
Value of the work
For the engineer: Practice cache correctness, request coalescing and capacity control.
For the team: Inspect whether faster delivery preserves bytes and operating 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.