Failure, Retry & Dead Letter Queue

Kill the Email service. Watch retries with backoff, messages land in the DLQ, the order stays green — then replay the DLQ.

Orders placed

never blocked

Emails delivered

In DLQ

Email consumer

● online

Place an order to send an OrderPlaced event here.

💀

Failed messages park here — safe, monitored, replayable.

Empty 🎉

What just happened

▹When Email is down, the broker retries with exponential backoff (0.8s → 1.6s) before giving up.
▹After max attempts the message parks in the Dead Letter Queue — it is never lost, and the order is never cancelled.
▹Fix Email, hit Replay DLQ, and the parked messages reprocess. Consumers must be idempotent so replays don't double-send.