Creating alarms for dead-letter queues using Amazon CloudWatch - Amazon Simple Queue Service
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Creating alarms for dead-letter queues using Amazon CloudWatch

Set up a CloudWatch alarm to monitor messages in a dead-letter queue using the ApproximateNumberOfMessagesVisible metric. For detailed instructions, see Creating CloudWatch alarms for Amazon SQS metrics. When the alarm triggers, indicating messages have been moved to the dead-letter queue, you can poll the queue to review and retrieve them.