SAA-C03 Design Resilient Architectures Practice Question
A warehouse integration service must process every event at least once, but duplicate processing is acceptable if the consumer handles idempotency. Which eventing approach is most suitable?
⚠ Common exam trap
Many exam-takers confuse 'at-least-once' with 'exactly-once' and incorrectly choose FIFO queues or other options, but the question explicitly accepts duplicates if idempotency is handled, making the standard queue the correct and simpler choice.
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
✓
Use Amazon SQS standard queue and design consumers to be idempotent
Amazon SQS standard queues provide at-least-once delivery, meaning each message is delivered at least once but can occasionally be delivered more than once. This matches the requirement to process every event at least once, and since duplicate processing is acceptable when consumers are idempotent, the standard queue is the most suitable and cost-effective choice. SQS also decouples the warehouse integration service from its consumers, improving resilience and scalability.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use CloudFront signed URLs
Why it's wrong here
CloudFront signed URLs are an access-control mechanism for content, not a message-delivery system. They provide time-limited authentication for viewers to retrieve objects, but they do not store, buffer, or retry events, and they cannot guarantee that a worker receives a particular event. If a signed URL request fails or expires, the event is simply missed, so this approach cannot ensure every event is processed.
- ✓
Use Amazon SQS standard queue and design consumers to be idempotent
Why this is correct
Amazon SQS standard queues provide at-least-once delivery with high throughput, meaning every message is delivered but occasional duplicates can occur. Designing consumers to be idempotent ensures that processing the same event multiple times yields the same result, which satisfies the requirement to process every event. This is the recommended pattern for reliable, scalable event processing in AWS.
- ✗
Use UDP messages sent directly to workers
Why it's wrong here
UDP is a connectionless, unreliable protocol that does not guarantee delivery, ordering, or duplicate suppression. Sending events directly to workers over UDP means messages can be dropped in the network or by the receiver without any acknowledgment or retransmission, so there is no way to ensure every event is processed. It also lacks durability and any built-in retry mechanism.
- ✗
Use an in-memory queue on one EC2 instance
Why it's wrong here
An in-memory queue residing on a single EC2 instance is volatile and creates a single point of failure. If the instance crashes, stops, or is terminated by Auto Scaling or Spot interruption, all queued events are lost permanently. Additionally, the instance's memory capacity becomes a bottleneck, and there is no cross-availability-zone redundancy to meet the requirement that every event must be processed.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SAA-C03 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SAA-C03 exam.