Replay a parser fix into a new projection generation
Parser v3 mislabeled ARRIVED_AT_DEPOT as DELIVERED. Operations needs to rebuild 100,000 synthetic scans while fresh batches continue arriving.
- Focused work estimate
- 5h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Replay architecture · Cutover consistency · Data repair · Operational safety
Estimated field mix
- Data engineering60%
- Distributed systems40%
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 delivery marketplace receives JSON batches from three carriers. One uses local timestamps, another retries whole batches, and a third corrects delivery scans. Customer support needs a stable timeline rather than the last payload received.
Setup prerequisites
- JSON schema validation
- SQL queries
- Event-time concepts
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
- PIPE-101 · Validate carrier events without discarding a whole batch
- PIPE-102 · Attach source lineage to every accepted scan
- PIPE-103 · Deduplicate carrier retries and surface changed duplicates
- PIPE-104 · Stop interpreting offset-free scans as server-local time
- PIPE-105 · Keep a late pickup scan from undoing delivered status
- PIPE-106 · Apply an explicit carrier correction without erasing the scan
Acceptance criteria
- Replay immutable sources into an isolated projection generation.
- Capture a high-water mark and include arrivals through the documented cutover boundary.
- Switch readers atomically only after counts and anomaly checks pass.
Implementation constraints
- Record parser and projection versions; rebuilding cannot mutate sources.
Verification to include
- Replay twice and compare deterministic output hashes.
- Interrupt replay and add events during catch-up; prove no cutover gaps.
Deliverables
- Replay command, generation cutover, and recovery runbook
Rollout and recovery
Keep the previous generation readable and revert its pointer if comparison fails.
Value of the work
For the engineer: Practice ingestion contracts, deduplication, event-time reconciliation, and replayable data repair.
For the team: Examine how an engineer preserves source lineage and handles bad partner data without losing valid business events.
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.