Prevent a late upgrade event from undoing a newer cancellation
Provider events arrive out of order and an old upgrade reopens collaboration after cancellation became effective.
- Focused work estimate
- 4h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Event ordering · Conflict handling
Estimated field mix
- Backend60%
- 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 document service grants storage and collaboration rights from subscriptions. Support cannot explain why delayed events restore old limits.
Setup prerequisites
- Create a local subscription API with synthetic accounts.
- Understand transactions and UTC intervals.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- Compare provider sequence within each subscription.
- Older events remain recorded without changing effective rights.
- Equal sequence with different payload is surfaced as conflict.
Implementation constraints
- Do not order provider events by receipt timestamp.
Verification to include
- Replay cancellation followed by an older upgrade.
- Submit contradictory equal-sequence events and preserve current rights.
Deliverables
- Ordering guard and conflicting-event report
Rollout and recovery
Run the guard in audit mode first; quarantine conflicts without deleting events.
Value of the work
For the engineer: Practice temporal rules, concurrency and explainable API decisions.
For the team: Review whether entitlement changes preserve customer access and produce supportable decisions.
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.