Consume messages from AWS SQS reliably using visibility timeout, a dead-letter queue, and idempotent processing

Steps

1. Create a standard or FIFO SQS queue; create a separate dead-letter queue (DLQ) of the same type and configure a redrive policy on the source queue specifying the DLQ ARN and maxReceiveCount (typically 3–5)
2. Set the queue's VisibilityTimeout to safely exceed your worst-case processing time; if processing can vary, extend visibility mid-flight using ChangeMessageVisibility before the timeout expires
3. Poll using ReceiveMessage with WaitTimeSeconds up to 20 (long polling) to reduce empty-receive API calls and cost; receive up to 10 messages per call (MaxNumberOfMessages=10)
4. Process each message and delete it via DeleteMessage using the ReceiptHandle only after successful processing — never delete before confirming success; undeleted messages become visible again after the visibility timeout
5. Implement idempotency keyed on the message MessageId or a business-level deduplication key stored in a database or ElastiCache; SQS standard queues deliver at least once and occasionally duplicate
6. Monitor ApproximateNumberOfMessagesNotVisible (in-flight), ApproximateAgeOfOldestMessage, and the DLQ depth in CloudWatch; alert on DLQ depth greater than 0