SAA-C03 Design Resilient Architectures Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✓

  Make the payment step idempotent using a unique transaction identifier.

  Why this is correct

  Correct. SQS provides at-least-once delivery, so the same message can be processed more than once if the worker times out, retries, or crashes after partially completing the work. An idempotency key lets the application recognize that the payment was already created and prevents duplicate charges.

• ✓

  Configure an SQS dead-letter queue with a redrive policy.

  Why this is correct

  Correct. Messages that fail validation repeatedly should not remain on the main queue forever, because they waste worker capacity and keep failing with the same error. A dead-letter queue isolates these poison messages after a configured number of receives so the team can inspect and remediate them separately.

• ✗

  Reduce the visibility timeout so failed messages return to the queue faster.

  Why it's wrong here

  Incorrect. Reducing visibility timeout speeds up redelivery, but it does not prevent duplicate business actions and can actually increase replay pressure. The core problem is that the payment operation must tolerate retries, and poison messages need a separate failure path.

• ✗

  Run only one long-lived worker instance so the queue can never be processed twice.

  Why it's wrong here

  Incorrect. A single worker reduces availability and still does not guarantee exactly-once processing, because SQS can redeliver messages after a timeout or failure. This approach makes the system less resilient and creates a single point of failure.

• ✗

  Switch from a standard queue to a FIFO queue and remove all other changes.

  Why it's wrong here

  Incorrect. FIFO queues help preserve order within a message group, but they do not remove the need for idempotent processing if the consumer times out after a partial success. They also do not replace the need for a dead-letter queue for messages that will never validate successfully.