Expose event ordering limits without requiring global sequencing
Partners assume events arrive in the order they happened, but parallel delivery reorders them.
- Focused work estimate
- 3h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Event ordering
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
- BAPIHOOK-105 · Document at-least-once delivery with stable event identities
- BAPIHOOK-106 · Bound retry scheduling and distinguish terminal receiver responses
Acceptance criteria
- Declare the actual ordering scope.
- Include resource revision where needed for stale-event handling.
- Document how receivers handle gaps and older revisions.
Implementation constraints
- Avoid promising global ordering without implementing it.
Verification to include
- Deliver two resource revisions out of order.
- Verify a receiver preserves its declared monotonic state.
Deliverables
- Ordering contract and receiver tests.
Rollout and recovery
Publish ordering guidance before increasing delivery parallelism.
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.