Amazon Simple Queue Service (Amazon SQS) is a pay-per-use web service for storing messages in transit between computers. Developers use SQS to build distributed applications with decoupled components without having to deal with the overhead of creating and maintaining message queues.
Amazon Simple Queue Service supports tasks that process asynchronously. Instead of one application having to invoke another application directly, the service enables an application to submit a message to a queue, which another application can then pick up at a later time.
An SQS queue can be FIFO (first-in, first-out) or standard. A FIFO queue maintains the exact order in which messages strings are sent and received. Standard queues attempt to preserve the order of messages, but can be flexible and when processing demands require it. FIFO queues provide exactly-once delivery, while standard queues provide at-least-once delivery.