Application Integration: SQS

A queue in the cloud

SQS is a highly-durable queue in the cloud. You put messages on one end, and a consumer takes them out from the other side. The messages are consumed in almost first-in-first-out order, but the ordering is not strict. The lack of strict ordering happens because your SQS queue is actually a bunch of queues behind the scenes. When you enqueue a message, it goes to a random queue, and when you poll, you also poll a random queue. In addition, duplicate messages can emerge within SQS, so your consumers should be prepared to handle this situation.