How can the developer ensure that the application processes each message exactly once?
Modify the SQS standard queue to an SQS FIFO queue.
Process the messages on one EC2 instance instead of three instances.
Create a new SQS FIFO queue. Point the application to the new queue.
Increase the DelaySeconds value on the current SQS queue.
Explanations:
SQS FIFO queues ensure message order and exactly-once processing within the same message group. However, changing from a standard queue to a FIFO queue may not guarantee exactly-once processing in this scenario without properly managing message groups and deduplication.
Using a single EC2 instance does not address the issue of multiple message processing. With a standard queue, messages can be delivered to multiple consumers, resulting in potential duplicates being processed.
A FIFO queue is designed to ensure exactly-once message processing. Switching to a FIFO queue will eliminate the possibility of multiple messages being processed more than once, as long as deduplication is correctly configured.
Increasing the DelaySeconds value will only delay the delivery of messages, not prevent duplicate processing. This does not address the core issue of multiple processing instances reading the same message.
In my opinion, the answer is:
Create a new SQS FIFO queue. Point the application to the new queue.