In an AWS SQS standard queue you can set a redrive policy which will cause messages to be retried if there is a failure where by the message is not deleted from the queue.
In my case i have > 1,000,000 messages on the queue which take a couple of hours to process. When a message fails and is put back on the queue will it be put to the end of the queue or the front. Will the messages get retried in a minute or two or in two or three hours when all the other messages have been processed?
There is no guarantee which order messages are returned, so once you return a message it could be retried immediately, when all the others are processed, or anywhere in the middle - there may be some undocumented common patterns for when retries happen, but its not something you can count on or design around.
Q: Does Amazon SQS provide message ordering?
Yes. FIFO (first-in-first-out) queues preserve the exact order in which messages are sent and received. If you use a FIFO queue, you don't have to place sequencing information in your messages. For more information, see FIFO Queue Logic in the Amazon SQS Developer Guide.
Standard queues provide a loose-FIFO capability that attempts to preserve the order of messages. However, because standard queues are designed to be massively scalable using a highly distributed architecture, receiving messages in the exact order they are sent is not guaranteed.
