Write a DNS change record with cache assumptions
The handoff omits when TTL was lowered and when old endpoints can be removed.
- Focused work estimate
- 1h + prerequisites
- Priority in the scenario
- Low
- Engineering practice
- Runbooks
Estimated field mix
- Networking70%
- 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
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.
- BDNS-101 · Inventory service records and their consumers
- BDNS-102 · Implement TTL-aware positive caching in the resolver fixture
- BDNS-103 · Model negative caching separately from empty address records
- BDNS-105 · Rehearse lowering TTL before endpoint cutover
- BDNS-106 · Preserve application compatibility across old and new addresses
- BDNS-104 · Reject alias loops and excessively deep resolution chains
- BDNS-107 · Distinguish resolver failure from application connection failure
- BDNS-108 · Evaluate rollback when both old and new answers remain cached
- BDNS-109 · Check IPv4 and IPv6 record migration independently
Acceptance criteria
- Record old/new values and effective times.
- List modeled cache and compatibility assumptions.
- Define endpoint retirement criteria.
Implementation constraints
- Use UTC timestamps and synthetic record identities.
Verification to include
- Follow the staged change from the record.
- Keep retirement blocked when a required client assumption is unknown.
Deliverables
- DNS cutover runbook.
Rollout and recovery
Preserve the change record after rollback or completion.
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.