A DLQ is used by other queues for storing failed messages that are not successfully consumed by consumer processes. You can use a DLQ to isolate unconsumed or failed messages and subsequently troubleshoot these messages to determine the reason for their failures.
SQS uses a redrive policy to indicate the source queue, and the scenario in which SQS transfers messages from the source queue to the DLQ. If a queue fails to process a message a predefined number of times, that message is moved to the DLQ.
While creating a queue, you can enable a redrive policy and set the DLQ name as well as maximum receive count, after which if the message is still unprocessed, it can be moved to the DLQ.
