Reconcile a create-event timeout before trying again
The calendar provider creates the appointment but drops its response. Retrying with a new request identifier currently creates a second event. Preserve creation identity and reconcile uncertainty.
- Focused work estimate
- 3h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Idempotency · External state reconciliation · Failure handling
Estimated field mix
- Integrations60%
- 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 consultancy books appointments across time zones. The first connector duplicates events after timeouts and offers slots during stale calendar sync. Use a local calendar-provider double and synthetic calendars.
Setup prerequisites
- Create a local provider double for free/busy, event creation, updates, cancellation, and expiring tokens.
- Use synthetic calendars and an injected clock; no calendar account or outgoing invitation is required.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- Each booking has a stable provider request identity persisted before the first call.
- A lost response triggers lookup by that identity or an explicit uncertain state when lookup is unsupported.
- A matching existing event is linked once; conflicting details block automatic completion.
Implementation constraints
- Use the local double to model accepted-then-timeout.
- Do not claim exactly-once provider behavior without the required idempotency contract.
Verification to include
- Lose the first create response and assert one provider event after reconciliation.
- Return an event with the same identity but different times and confirm the booking enters conflict without another create.
Deliverables
- Idempotent creation adapter and uncertain-outcome tests
Rollout and recovery
Require reconciliation support before enabling retries; unsupported providers remain in manual resolution on ambiguous outcomes.
Value of the work
For the engineer: Practice time modeling, conflict-safe booking, external state reconciliation, and credential lifecycle boundaries.
For the team: Review whether integration work protects appointment correctness and offers clear recovery when a provider is uncertain.
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.