Apply an explicit carrier correction without erasing the scan
A driver scanned the wrong parcel as delivered. The carrier now sends corrections referencing the original scan; support must see why Delivered became In transit.
- Focused work estimate
- 3h 30m + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Append-only models · Referential integrity · Event correction
Estimated field mix
- Data engineering70%
- Database engineering30%
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
Acceptance criteria
- Require a same-carrier, same-parcel target event.
- Keep the original scan and append the correction relationship.
- Recompute the projection and expose the withdrawn delivery scan.
Implementation constraints
- Missing targets become pending references with bounded retry, never permission to delete arbitrary events.
Verification to include
- Apply a valid delivery withdrawal and inspect history and state.
- Reject a cross-parcel target and resolve a target that arrives later.
Deliverables
- Correction contract and deferred-reference recovery
Rollout and recovery
Enable the configured correction-capable carrier; retain history if projection readers are rolled back.
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.