An orders service publishes payment instructions to an Amazon SQS Standard queue. The downstream processor sometimes times out after it has already applied the payment, but before it can delete the message from the queue. As a result, the same payment instruction can be processed more than once. The team wants the strongest way to prevent duplicate side effects while keeping the system decoupled. What should they implement?

Keep the queue as SQS Standard but increase the visibility timeout so duplicates are less likely to reappear during timeouts.

Increasing visibility timeout only delays redelivery. If DeleteMessage fails, the message can still become visible again and be processed again.

Change the queue to an SQS FIFO queue and use a stable deduplication ID derived from the payment instruction ID.

FIFO deduplication reduces duplicate sends within the deduplication window, but it does not prevent a message already in flight from being redelivered after the visibility timeout if it was not deleted.

Use an ALB health check to restart the downstream processor when timeouts occur.

Restarting the processor may help availability, but it does not change SQS delivery semantics or prevent a redelivered message from causing duplicate side effects.

What does this SAA-C03 question test?

Static NAT maps one inside address to one outside address.

What is the correct answer to this question?

The correct answer is: Make the downstream processor idempotent by recording processed payment instruction IDs in a durable datastore and ignoring repeats. — Because SQS Standard provides at-least-once delivery, a message can be delivered again if the consumer applies the payment but fails to delete the message before the visibility timeout expires. The strongest protection is to make the consumer idempotent: persist a durable record of processed payment instruction IDs and ignore repeats. That prevents duplicate side effects regardless of how many times the queue redelivers the message. A longer visibility timeout only postpones retries and does not eliminate redelivery. FIFO deduplication helps with duplicate sends, but it does not stop redelivery of an already enqueued message that was not deleted. Restarting the worker via health checks does not change queue semantics or duplicate-processing risk.

What should I do if I get this SAA-C03 question wrong?

Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.