Dead Letter Queue
In plain terms
A holding area for messages that couldn't be processed successfully.
Going deeper
When a message repeatedly fails handling, it's moved to a dead letter queue for inspection instead of blocking the main flow or being lost. It aids debugging and reliability in messaging systems.
Under the hood
Captures messages that exceed retry limits for later inspection or reprocessing, preventing poison messages from blocking the pipeline.
Examples
AWS SQS DLQ, RabbitMQ dead-letter exchange, Kafka error topics.
Think of it like...
Like a post office's undeliverable-mail bin: letters that can't be delivered are set aside for review rather than clogging the route or vanishing.