Transactional Outbox Pattern

The pattern that solves the dual-write problem — ensuring your database write and event publish either both happen or neither does.

Key Takeaways

1. The outbox pattern ensures database writes and event publishing happen atomically — write both to the same database transaction, then publish events asynchronously
2. Solves the dual-write problem — without it, a crash between database commit and event publish leaves the system in an inconsistent state
3. A background process (poller or CDC) reads from the outbox table and publishes events — Debezium with CDC is the most reliable approach
4. Events in the outbox must be published in order and at-least-once — consumers must be idempotent to handle duplicate deliveries