While working in one of the project I recently came across the problem. The problem was that the data I push in queue is not coming in the same order I push it in. I thought of it as a callback problem with my JS code but when I tried more I came to realise its not my code. Then I read about the FIFO queues.
AWS provides two queues in SQS service one is normal queue and the other one is FIFO queues. The normal queues ensures delivery but not in the order you inserted into it. While FIFO queues ensures the order in which you pushed the message into the queue. This is the reason these queues are bit costly than the normal queue.
Also when I am writing this article these queues are available in US East (N. Virginia), US East (Ohio), US West (Oregon), and EU (Ireland) regions only. They are awaited to be launched in other region in coming months.
You can read more about them in their official documentation.