SQS DLQ Incident Workflow

When downstream consumers fail to process messages, those messages land in a Dead Letter Queue (DLQ). A DevOps Engineer Professional must know how to detect, alarm on, and remediate poison-message scenarios before the DLQ becomes a black hole of lost data.

In this lab you will:

• Create an SQS Standard Queue with a redrive policy that routes failed messages to a DLQ after 3 receive attempts
• Build a Python Lambda that processes messages and simulates poison-message failures when a message body contains "FAIL"
• Wire the Lambda as an SQS event source and observe normal messages being processed while poison messages accumulate in the DLQ
• Create a CloudWatch alarm on the DLQ's ApproximateNumberOfMessagesVisible metric and notify an SNS topic
• Build a DLQ redrive Lambda that inspects DLQ messages and redrives them back to the main queue for reprocessing
• Simulate a full incident: send poison messages, verify DLQ alarm fires, redrive messages, and confirm successful reprocessing

Every resource is tagged with lab=true and Course=dop-c02. All operations use the AWS CLI in us-east-1.