An application needs to make use of a messaging system. The messages need to be processed in the order they are received, and also no duplicates should be allowed. Which of the following would you use for this purpose?

Answer options:

A.Enable FIFO on an existing SQS Standard Queue.
B.Add the .fifo extension to the existing Standard SQS Queue.
C.Consider using SNS.
D.Use the FIFO SQS Queues.

Answer – D
This is also mentioned in the AWS Documentation.
FIFO (First-In-First-Out) queues are designed to enhance messaging between applications when the order of operations and events is critical or where duplicates can`t be tolerated, for example:
Ensure that user-entered commands are executed in the right order.
Display the correct product price by sending price modifications in the right order.
Prevent a student from enrolling in a course before registering for an account.
Options A and B are incorrect since an existing Standard queue can`t be changed to FIFO.
Q: Can I convert my existing standard queue to a FIFO queue?
No. You must choose the queue type when you create it. However, it is possible to move to a FIFO queue.
Option C is incorrect since this is a notification service and not a queuing service.
For more information on SQS FIFO Queues, please refer to the below URL-
https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/FIFO-queues.html