SQS

Amazon SQS is AWS’s managed message queue. A producer writes messages, and one or more consumers poll for them. Each message is processed once and then deleted. A queue absorbs bursts and outages, which makes it the default way to decouple a producer that cannot wait from a consumer that cannot always keep up.

SQS covers the choices that matter when designing with a queue: standard versus FIFO, message size and retention, the visibility timeout, polling, and throughput limits.

Every queue design also needs an answer for the message that fails repeatedly. Dead-letter queues explains how to set aside messages that cannot be processed, how to redrive them once the fault is fixed, and which CloudWatch metrics actually signal a problem.