A dead-letter queue (DLQ) receives messages that exceed a configured number of unsuccessful processing attempts. It preserves failed work for later inspection or handling. section 16.3.4
In a fault-tolerant web application, the DLQ:
- Appears beside an SQS queue in the Imagery application’s infrastructure. section 16.3.4
- Is deployed with S3, DynamoDB, EC2 Auto Scaling groups, an Application Load Balancer, and IAM roles through CloudFormation. section 16.3.4
Deploy the surrounding SQS-based application by creating the Imagery CloudFormation stack from the terminal. section 16.3.4



