How do you implement a dead letter queue (DLQ) pattern in Kafka?

A dead letter queue (DLQ) in Kafka handles messages that cannot be processed after exhausting retries, preventing them from blocking the consumer or being silently dropped. Implementation: Consumer retry loop: catch processing exceptions, retry N times. After N failures, produce the failed message to a dedicated topic-name.DLQ topic. Include the original message plus error metadata (exception, timestamp, consumer group, original offset) in headers or envelope. Kafka Connect DLQ: built-in DLQ support in connectors — set errors.deadletterqueue.topic.name=topic.DLQ and errors.tolerance=all. Spring Kafka: configure DefaultErrorHandler with a DeadLetterPublishingRecoverer. Monitor the DLQ and alert when messages appear — they indicate a systemic processing failure. Build a DLQ replay tool to reprocess messages after fixing the underlying bug.