Kafka

Question: What happens if Kafka is down when your Command service tries to publish an event?

• The Staff Answer: * The Danger: If the service finishes the DB transaction but fails to send the Kafka event, the system enters an inconsistent state.

  • The Solution: The Transactional Outbox Pattern. We save the Order AND the Event into the same database transaction. A separate process (like a polling thread or Debezium) then polls the OUTBOX table and pushes events to Kafka. If Kafka is down, the polling process just keeps retrying until success.