Model negative caching separately from empty address records
A temporary missing hostname remains unavailable after its record is created.
- Focused work estimate
- 3h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- DNS · Failure analysis
Estimated field mix
- Networking80%
- Site reliability20%
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
- Distinguish nonexistent name from no record of requested type.
- Apply declared negative-cache lifetime.
- Preserve the reason for cached negative answers.
Implementation constraints
- Use explicit fixture policy rather than claiming universal resolver behavior.
Verification to include
- Create a record after a negative lookup.
- Show recovery only after the modeled negative cache expires.
Deliverables
- Negative-cache scenarios.
Rollout and recovery
Avoid deleting names during cutover unless negative-cache effects are accepted.
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.