Stop duplicate and out-of-order notes confusing the timeline
A reconnect overlaps live delivery with replay. The same mitigation note appears twice, and a late earlier event moves a resolved task back to active.
- Focused work estimate
- 2h 30m + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Event ordering · Deduplication · State consistency
Estimated field mix
- Real-time systems60%
- 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
The fictional Harbor operations team coordinates synthetic incidents in a shared room. Engineers post status notes and claim response tasks while connections come and go. Scope is one application gateway, a durable room event store, and fixture clients; alert paging and external chat delivery are excluded.
Setup prerequisites
- Room membership and command contracts
- Synthetic incident events and a controllable transport harness
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- Event identity deduplicates replay and live delivery for the same room.
- Only a contiguous server sequence advances the applied cursor.
- Out-of-order gaps are buffered within a configured bound and trigger recovery rather than arbitrary state application.
Implementation constraints
- A wall-clock timestamp is presentation metadata, not the authoritative event order.
Verification to include
- Deliver a duplicate event through replay and live paths; the timeline shows it once.
- Deliver sequences 12, 14, 13 and then an oversized gap; apply contiguous state correctly and enter recovery at the bound.
Deliverables
- Ordered room reducer and duplicate/gap test vectors
Rollout and recovery
Shadow the reducer against fixed logs before use; reset from a validated snapshot if gap recovery fails.
Value of the work
For the engineer: Practice event identity, ordering, replay, authorization, and bounded backpressure in one understandable system.
For the team: Inspect how an engineer keeps collaborative state trustworthy during failures without relying on optimistic success messages.
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.