Document at-least-once delivery with stable event identities
The platform advertises one delivery even though connection loss can cause duplicates.
- Focused work estimate
- 3h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Distributed systems · Idempotency
Estimated field mix
- Distributed systems60%
- API 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 logistics platform sends shipment events to partner endpoints. Partners need stable schemas and recovery semantics despite duplicate delivery, failures, and subscription changes.
Setup prerequisites
- Create a local webhook sender and receiver doubles with synthetic shipment events and disposable signing keys.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
- BAPIHOOK-101 · Define immutable webhook envelopes independently of database rows
- BAPIHOOK-102 · Authorize subscription creation and event scope per organization
- BAPIHOOK-103 · Validate webhook destinations through the restricted network boundary
- BAPIHOOK-104 · Sign exact webhook bytes with versioned verification metadata
Acceptance criteria
- Keep event identity stable across attempts.
- Record delivery attempts separately from event facts.
- Provide a receiver deduplication example.
Implementation constraints
- Do not claim exactly-once delivery across HTTP.
Verification to include
- Lose a receiver acknowledgement and retry.
- Verify the receiver applies the event once using its deduplication record.
Deliverables
- Delivery semantics and replay checks.
Rollout and recovery
Preserve event identity through all retries and support actions.
Value of the work
For the engineer: Practice public event contracts, delivery guarantees, and partner recovery workflows.
For the team: Provide inspectable asynchronous integration behavior with controlled retries and clear compatibility.
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.