Deduplicate carrier retries and surface changed duplicates
Carrier Cedar retries yesterday's batch. Most event IDs are identical, but one delivery timestamp changed from 14:03 to 14:30 and is overwritten silently.
- Focused work estimate
- 2h 30m + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Idempotency · Unique constraints · Provenance
Estimated field mix
- Data engineering60%
- Database engineering40%
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.
Acceptance criteria
- Identical carrier-scoped event IDs and content replay without duplicate scans.
- Changed content under an existing ID enters a conflict record.
- Concurrent duplicate imports converge to one accepted event.
Implementation constraints
- An event ID from another carrier is a separate identity.
Verification to include
- Replay the batch twice and compare accepted counts.
- Submit changed content and concurrent duplicates; inspect originals and conflicts.
Deliverables
- Deduplication constraint and conflict handling contract
Rollout and recovery
Observe duplicate classifications before enforcement; preserve originals if conflict routing is 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.