Implement TTL-aware positive caching in the resolver fixture
The simulator caches every answer forever and cannot represent migration delays.
- Focused work estimate
- 2h + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- Caching · DNS
Estimated field mix
- Networking60%
- Performance engineering40%
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 internal API is moving to a new endpoint. The team assumes DNS changes are immediate and has no rehearsal for stale clients.
Setup prerequisites
- Create a local resolver simulator and two loopback service endpoints with synthetic DNS records; query no external infrastructure.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- Expire answers using an injected clock.
- Honor the declared TTL without extending it on reads.
- Key cache entries by name and record type.
Implementation constraints
- Do not use wall-clock sleeps in tests.
Verification to include
- Serve a cached answer before expiry.
- Advance time and retrieve the changed authoritative answer.
Deliverables
- Positive-cache simulator.
Rollout and recovery
Validate the simulator against its documented semantics before using results.
Value of the work
For the engineer: Practice DNS semantics, migration timing, and network diagnosis.
For the team: Produce a migration plan that makes cache delay and endpoint compatibility explicit.
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.