Design per-channel attempt identity and provider reconciliation
The email provider times out after accepting a request; retrying blindly sends the same message twice.
- Focused work estimate
- 5h + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- Distributed contracts · Uncertainty
Estimated field mix
- Distributed systems60%
- System design40%
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 collaboration tool sends email and in-app notifications. Duplicate alerts and preference changes reveal that the design has no single definition of delivery.
Setup prerequisites
- Create synthetic recipients, events and fake delivery providers.
- Do not send real email or messages.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
- ANOTIFY-101 · Separate notification intent from channel delivery and human receipt
- ANOTIFY-102 · Specify recipient resolution without copying event payloads broadly
- ANOTIFY-103 · Choose when notification preferences are evaluated
- ANOTIFY-104 · Model notification intent and dispatch in one durable transaction
Acceptance criteria
- Bind each logical channel delivery to a stable provider key.
- Represent unknown acceptance and define a status lookup path.
- Document provider limitations that prevent exactly-once claims.
Implementation constraints
- The local fake must support accepted-but-response-lost behavior.
Verification to include
- Reconcile lost response to one accepted synthetic delivery.
- Use a provider without lookup support and retain an explicit uncertain state.
Deliverables
- Channel contract and uncertainty probe
Rollout and recovery
Select adapters only after contract review; stop automatic retries where duplicate risk is unresolved.
Value of the work
For the engineer: Practice asynchronous contracts, preference timing and delivery uncertainty.
For the team: Review a notification design that controls nuisance, disclosure and recovery.
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.