CTIER-102 · Define cache reads

Key archive cache entries by immutable blob identity

Practice briefTaskFoundational

A mutable filename reuses stale cached bytes after replacement. Bind entries to immutable version or digest.

Focused work estimate: 1h 15m + prerequisites
Priority in the scenario: Medium
Engineering practice: Caching · Identity

Estimated field mix

Storage systems70%
Performance engineering30%

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.

CTIER-101 · Keep archive cache misses distinct from provider failures

Acceptance criteria

Same identity reuses entry
New version uses new key
User labels do not affect identity

Implementation constraints

Tenant scope remains part of lookup authority.

Verification to include

Read repeated identity
Replace logical filename with new version

Deliverables

Cache-key contract and cases

Rollout and recovery

Disable cache reuse if identity is uncertain.

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.