A system processes events from Amazon SQS and sometimes sees duplicate messages due to retries. The business requirement is that each payment must be charged at most once. What design choice best addresses this resiliency requirement?

Assume duplicates never occur because the consumer deletes messages immediately after receiving them.

With SQS at-least-once delivery, duplicates can still occur if processing fails, times out, or crashes before the delete occurs. Even if you delete quickly after receiving, failures after the side effect can still lead to duplicates being delivered later.

Increase the SQS visibility timeout until duplicates never happen.

Changing visibility timeout only affects when messages are retried. It does not change SQS’s delivery semantics or guarantee that duplicates will never be delivered, nor does it prevent duplicate side effects from being executed.

Use SNS topics instead of SQS so retries are disabled by default.

Switching to SNS does not guarantee exactly-once processing for downstream systems. Duplicate notifications and retries can still occur due to delivery failures and subscriber behavior, so idempotency is still required to enforce at-most-once charging.

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: Implement idempotent processing using a deduplication key (for example, paymentId) and record completed charges so duplicates are safely ignored. — Implement idempotent processing. Because SQS is at-least-once, a message can be delivered more than once (for example, if the consumer crashes after charging but before deleting the message). To ensure each payment is charged at most once, use an idempotency key such as paymentId and persist an indicator of completion in a datastore that supports safe uniqueness (for example, a unique constraint in a relational database or a conditional write in a key-value store). When the same paymentId is received again, the consumer skips the charge operation. At-least-once delivery means duplicates can still appear depending on failures and the timing of deletes/acknowledgements. Increasing visibility timeout changes retry timing but does not eliminate duplicates or prevent duplicate side effects. Replacing SQS with SNS does not inherently provide exactly-once end-to-end behavior for payment charging.

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.