Handoff a preference snapshot to live changes without a gap
A new replica loads a snapshot while preferences continue changing, leaving a gap between export time and stream start.
- Focused work estimate
- 6h + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- Snapshot consistency · Recovery
Estimated field mix
- Data engineering50%
- Distributed systems50%
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 messaging service builds a read model from database changes. Restarts and schema changes can re-enable preferences that customers disabled.
Setup prerequisites
- Create synthetic preference records and a replayable local change log.
- Use adapters or fixtures without provisioning a production broker.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- Record an explicit snapshot boundary position.
- Buffer or replay changes after the boundary before activation.
- Keep the new generation unavailable until catch-up is complete.
Implementation constraints
- Document source guarantees needed for a consistent boundary.
Verification to include
- Change a preference during snapshot loading and reach final source state.
- Interrupt catch-up and verify readers still use the previous generation.
Deliverables
- Snapshot handoff protocol and executable timeline
Rollout and recovery
Build a shadow generation; restore the previous pointer if catch-up checks fail.
Value of the work
For the engineer: Practice change-feed ordering, snapshots and privacy-preserving deletion.
For the team: Review whether replicated customer preferences remain correct during recovery.
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.