Ignore duplicate calendar notifications and detect missed updates
Provider notifications arrive twice, then a subscription expires and updates stop. Treat notifications as sync hints and maintain a separate reconciliation cursor and subscription deadline.
- Focused work estimate
- 2h 30m + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Webhook security · Cursor sync · Freshness · Idempotent jobs
Estimated field mix
- Integrations40%
- Distributed systems30%
- Security30%
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.
- CAL-101 · Reject local times that do not identify one instant
- CAL-102 · Merge overlapping busy intervals before offering slots
- CAL-103 · Label unavailable or stale free/busy data instead of showing open slots
- CAL-104 · Reserve a slot atomically when two customers choose it
- CAL-105 · Reconcile a create-event timeout before trying again
- CAL-106 · Move a booking only if its current revision still matches
- CAL-107 · Make repeated cancellation safe and tenant scoped
- CAL-108 · Refresh expired connector credentials once per account
Acceptance criteria
- Authenticated duplicate notifications schedule at most one active sync for the connector.
- Sync advances its provider cursor only with committed local changes.
- Expired subscriptions or invalid cursors trigger an explicit refresh/reconnect path and mark availability stale.
Implementation constraints
- Validate the local notification authentication contract before trusting connector metadata.
- Do not use notification arrival order as event revision order.
Verification to include
- Send duplicate and invalid-auth notifications and count scheduled jobs.
- Expire a subscription and invalidate a cursor; confirm availability becomes unbookable until a successful resync.
Deliverables
- Notification ingestion, sync checkpointing, and expiry scenarios
Rollout and recovery
Enable notification ingestion alongside periodic reconciliation; pause booking when either path cannot establish fresh availability.
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.