/aws/sqs
A durable message queue. Producers push messages; workers pull them. Each message is processed by exactly one worker. Built-in retries via visibility timeout, dead-letter queues for poison messages, retention up to 14 days. The default answer for "distribute this work" or "buffer this burst so the API can accept it now and workers can catch up."
Both make your system asynchronous, but they solve different problems. Queue semantics vs topic semantics, when to reach for each, and the SNS → SQS fan-out pattern that shows up in real system designs.
Build the SNS-to-SQS fan-out pattern where each consumer owns a private queue with its own retry policy and DLQ. Covers queue policies, raw message delivery, redrive config, and the delivery guarantees you actually get.