Enforce archive cache capacity before admitting a fill
Parallel fills exceed the configured cache budget because each sees free space. Reserve capacity atomically.
- Focused work estimate
- 3h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Capacity planning · Concurrency
Estimated field mix
- Storage systems50%
- Performance 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
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
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- Active reservations count toward limit
- Failed fills release reservation
- Oversized objects bypass with explanation
Implementation constraints
- Include temporary bytes in capacity accounting.
Verification to include
- Admit fitting concurrent fills
- Attempt object larger than budget
Deliverables
- Admission reservations and cases
Rollout and recovery
Stop cache admission until accounting reconciles.
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.