SAA-C03 Design Resilient Architectures Practice Question
A financial services firm runs a batch settlement job on a fleet of Amazon EC2 instances that pull work from an Amazon SQS queue. The job must not lose messages if an instance is terminated mid-processing, and duplicate processing must be minimized because each settlement charge is expensive. The team also wants to avoid indefinite reprocessing of a message that repeatedly fails. Which two changes should the solutions architect make to meet these requirements? (Choose two.)
⚠ Common exam trap
The trap here is assuming that switching to a FIFO queue alone guarantees no duplicates, when the visibility timeout and a dead-letter queue are what actually control redelivery and poison messages.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Increase the queue's visibility timeout so it exceeds the maximum expected processing time.
Raising the visibility timeout above the maximum processing time prevents a still-running message from being redelivered to another consumer, which directly reduces duplicate settlement charges. Attaching a dead-letter queue with a maximumReceiveCount moves repeatedly failing messages aside after a set number of receives, so they are not reprocessed indefinitely while healthy traffic continues.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Switch the queue to an Amazon SQS FIFO queue with content-based deduplication.
Why it's wrong here
A FIFO queue provides exactly-once processing within a deduplication interval, but switching queue type changes ordering and throughput characteristics, and content-based deduplication only suppresses identical message bodies within a five-minute window. It does not address the visibility timeout or the need to stop reprocessing a repeatedly failing message.
- ✓
Increase the queue's visibility timeout so it exceeds the maximum expected processing time.
Why this is correct
If the visibility timeout is shorter than the processing time, the message becomes visible again and a second consumer can pick it up, causing duplicate settlement charges. Setting the timeout above the worst-case processing duration prevents this overlap and is essential for minimizing duplicates in a pull-based worker fleet.
- ✗
Store a processing flag in an Amazon ElastiCache for Redis cluster and check it before charging.
Why it's wrong here
Adding an external deduplication store introduces another component that can fail and must be kept consistent with the queue, increasing operational risk. It also does not stop a poison message from being redelivered forever. Native queue controls are simpler and more reliable for these requirements.
- ✗
Enable long polling on the queue by setting ReceiveMessageWaitTimeSeconds to 20.
Why it's wrong here
Long polling reduces empty responses and cost by waiting for messages, but it has no effect on duplicate processing or on stopping a poison message. It is a cost and efficiency optimization rather than a correctness control, so it does not satisfy either stated requirement for this settlement workload.
- ✓
Configure a dead-letter queue on the source queue with a maximumReceiveCount.
Why this is correct
A dead-letter queue captures messages that exceed the configured receive count, so a persistently failing message stops being redelivered indefinitely. This satisfies the requirement to avoid endless reprocessing and lets the team inspect failures separately, while normal messages continue to flow through the main queue.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
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