Aglet

How to learn from missing-event delivery gaps and recovery

Missing-event learning records the path a source change must travel and the evidence required at each boundary. Keep event identity, version, delivery ownership, retry and replay rules, projection outcome, and the customer-visible contract together for every supported downstream consumer path.

Keep the lesson for the next incident

  1. Document the event delivery contract

    Describe source commit, event creation, identifier and version, acceptance, consumer claim, handler success, acknowledgment, projection or notification update, and visible outcome. State which failures retry, which require review, and how duplicate delivery is safe. Keep payload examples structural and redacted.

  2. Keep an end-to-end gap journey

    Preserve checks for normal delivery, producer failure, consumer failure, projection failure, retry, replay, duplicate prevention, ordering, and final visibility. Define expected evidence at every boundary. Assign ownership for interpreting a missing event and for updating the journey when consumers change.

  3. Recheck after schema or route changes

    Review the cases after event schema, routing, filters, producers, consumers, acknowledgments, projection writes, or replay tooling change. Compare event identity and downstream state again. Add a distinct case when a new consumer has a different durability, ordering, or recovery contract.

What to carry forward

The learning record should retain event identity and versions, boundary evidence, consumer and replay ownership, downstream contracts, and recurrence triggers. It is complete when future engineers can distinguish missing emission from delayed outcome and can recover without creating duplicates.

Keep the decision with the work.

Use a Work Item in Aglet to record the problem, the evidence you have, and the next decision. Add an owner and priority, then keep updates in the discussion so the next person can follow the reasoning.

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