Outbox Pattern

Problem

Your service does: 1. Save Order 2. Publish OrderCreated The database save succeeds. Then the process crashes before publishing. Now the order exists but nobody receives the event.

Solution — Transactional Outbox

Save the business change and outgoing event record in the same database transaction.

Transaction:
  Order
  +
  Outbox event
      ↓ later
Publisher → Broker

Core idea: the outbox pattern closes the consistency gap between database changes and message publication.