A failed Lambda function invokes asynchronously by default. It is retired twice. Then, the Lambda function event is discarded. AWS Lambda gets an indication to use DLQ for the unprocessed events. These unprocessed events send you to an Amazon SNS topic or an Amazon SQS queue where you will take further action.
You can configure DLQ by mentioning a target Amazon Resource Name (ARN) in the DeadLetterConfig parameter in the Lambda function for the Amazon SQS queue or Amazon SNS topic where the event payload will be delivered. Functions without any association with DLQ discard those events after exhausting their retries.
To access your DLQ resources, you need to provide explicitly receive and/or delete and/or sendMessage ...
