Persist replacement progress across stock reservation and shipment creation
A replacement reserves the last unit, then shipment creation fails. Retrying from the beginning makes another reservation, while immediately issuing a refund would ignore stock still held for the customer.
- Focused work estimate
- 4h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Workflow orchestration · Compensation · Uncertain outcomes
Estimated field mix
- Distributed systems60%
- Integrations20%
- Backend20%
Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence.
Pattern topics
- SagaApply
Coordinate durable replacement steps and fallible compensation so a partial provider success can be resumed or reconciled without repeating earlier effects.
- StateApply
Represent uncertain provider outcomes separately from confirmed failures so workflow transitions cannot invent a successful rollback or completed refund.
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Project context
A fictional equipment retailer lets customers choose a refund or replacement after inspection. Its payment and stock providers can time out after accepting an operation, so retrying the whole return is unsafe. Create a local TypeScript application, PostgreSQL state/outbox tables, and synthetic provider doubles with controllable outcomes; no starter code or fixtures are supplied. Use invented orders and integer minor-unit amounts only, with no real payments or external provider calls.
Setup prerequisites
- SQL transactions
- Idempotent commands
- Async failure handling
- State modeling
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- Persist separate reservation and shipment steps with stable provider operation keys and explicit pending, confirmed, failed, and uncertain outcomes.
- Resume from recorded progress after restart; a confirmed reservation is reused instead of repeated when shipment creation is retried.
- On a confirmed shipment failure, schedule release of the reservation before offering the declared refund fallback; uncertain effects remain unresolved until checked.
Implementation constraints
- Use a durable orchestrated workflow in the local application; compensation is another fallible operation, not a database rollback of an external effect.
Verification to include
- Reserve stock, crash before shipment confirmation, and resume; assert one reservation lineage and the correct next step.
- Return a confirmed shipment rejection and then a reservation-release timeout; verify the workflow remains visible and does not silently refund or reserve again.
Deliverables
- Replacement step model and reservation/shipment recovery cases
Rollout and recovery
Enable the replacement path for one synthetic order type; pause new workflows while allowing existing recorded steps to reconcile on rollback.
Value of the work
For the engineer: Practice durable workflow state, ambiguous provider outcomes, compensation, concurrency isolation, and recovery that survives process restarts.
For the team: Inspect whether a proposed workflow preserves refund and inventory invariants, contains provider failures, and gives operators a bounded recovery path.
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.