The use case that you described is well-suited for SQS: instead of prrocessing a long running task directly upon API request, you instead send a message with the request payload to an SQS queue so that it can be processed layer. But SQS does not trigger any lambda function per se, in the end you have a queue allowing you to send a message to it and this message can then be picked up and processed by some other process (pool of workers or perhaps another lambda function running on schedule and regularly processing messages from the queue etc).