Detect overlapping booking attempts against one availability revision
Two bookers see the same open slot before either reservation is committed.
- Focused work estimate
- 3h 30m + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Concurrency · Scheduling
Estimated field mix
- Database engineering40%
- Integrations30%
- Distributed systems30%
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 booking service supports consultants in multiple time zones. Recurring events, revoked access, and delayed callbacks cause missed conflicts.
Setup prerequisites
- Author synthetic calendars and a local provider double with recurrence, timezone, and access-revocation cases.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
- BCALENDAR-101 · Distinguish all-day events from timed calendar intervals
- BCALENDAR-102 · Resolve daylight-saving gaps and repeated local times
- BCALENDAR-103 · Expand recurrence within a bounded availability window
- BCALENDAR-104 · Apply event revisions without reviving cancelled occurrences
- BCALENDAR-106 · Project busy intervals without exposing event descriptions
- BCALENDAR-105 · Use incremental sync tokens without losing full-resync coverage
- BCALENDAR-107 · Stop provider calls immediately after access revocation
Acceptance criteria
- Bind booking checks to a declared availability revision.
- Serialize or atomically reject overlapping local reservations.
- Represent external confirmation as pending when unknown.
Implementation constraints
- Use a local provider double; create no real events.
Verification to include
- Race two bookings for one slot.
- Change provider availability during booking and expose the conflict.
Deliverables
- Booking consistency checks.
Rollout and recovery
Keep short local reservations; reconcile unknown external outcomes before releasing them.
Value of the work
For the engineer: Practice temporal modeling, synchronization lifecycles, and privacy-preserving projections.
For the team: Reduce scheduling ambiguity through explicit availability contracts and recoverable synchronization.
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.