Error Handling & Dead Letter Topics

Produce JSON keyed by userId for ordering, consume with manual ack plus bounded retries plus a DLT for safety, batch-listen for throughput, and pause/resume on downstream health.

A poison pill blocks the partition forever on a record that can never succeed, so after bounded retries you route it to a dead letter topic, commit past it, and keep the partition flowing.

A Dead Letter Topic is a dedicated Kafka topic where messages that fail processing after all retries are sent for later inspection and recovery.

@RetryableTopic gives non-blocking retries through separate retry topics with growing backoff ending in a dead letter topic, where retry topics reprocess after a delay and the DLT is terminal.

Redrive moves dead letter records back to the main flow under operator control, and it is safe only when consumers are idempotent and you inspect, selectively replay, or discard rather than blindly pushing everything back.

A dead letter queue only isolates failures; handling them requires monitoring, classification, a replay procedure, and ownership, so treat it as an incident-response mechanism, not a config flag.