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? The architecture review board prefers a managed AWS-native control.
⚠ Common exam trap
Test-takers frequently confuse 'at-least-once' delivery with 'exactly-once' delivery and incorrectly choose a solution like FIFO queues (not listed) or dismiss SQS standard queues due to the duplicate processing allowance, but the question explicitly states duplicates are acceptable if idempotency is handled, making SQS standard the correct 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, which guarantees that every message is processed at least once, meeting the requirement that every event must be processed. Duplicate processing is acceptable because the consumer can be designed to handle idempotency. This is a managed, AWS-native service that aligns with the architecture review board's preference.
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 a mechanism for controlling access to content distributed through Amazon's CDN, typically by appending authentication parameters to HTTP requests. They only govern whether a client can retrieve a specific object; they carry no payload, no delivery semantics, and no persistence for application events. As a result, they cannot guarantee that every warehouse integration event is delivered to a processing worker.
- ✓
Use Amazon SQS standard queue and design consumers to be idempotent
Why this is correct
An SQS standard queue is designed for decoupling components and provides at-least-once delivery with high throughput, ensuring that every message placed in the queue is eventually delivered to a consumer. Because at-least-once delivery can produce duplicate messages, consumers must be built to process each event idempotently so that repeated handling does not corrupt state or create duplicate outcomes. This combination satisfies the requirement that every event is processed.
- ✗
Use UDP messages sent directly to workers
Why it's wrong here
UDP is a lightweight, connectionless transport protocol that offers no acknowledgements, retransmissions, or ordering guarantees, so datagrams can be dropped silently in the network. Without built-in durability or a re-delivery mechanism, transmitting integration events directly to workers over UDP risks losing events entirely, which directly violates the need to process every event.
- ✗
Use an in-memory queue on one EC2 instance
Why it's wrong here
Maintaining an in-memory queue on a single EC2 instance means all pending events exist only in that instance's volatile RAM; if the instance crashes, is stopped, or terminates, the entire queue and its events are permanently lost. This approach creates a single point of failure, offers no horizontal scaling, and lacks any persistence layer, making it unsuitable for a service that must reliably process every event without loss.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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