Introduction to the Transactional Outbox Pattern

In the Saga Pattern chapter, each step commits a local transaction and then publishes an event. That sentence hides a hard problem. The commit and the publish are two separate actions on two separate systems. If one succeeds and the other fails, your services disagree about what happened. The Transactional Outbox Pattern exists to remove that risk.

What the Pattern Says

An outbox is a table in the service's own database where the service writes each event as a row