- A
Delete the SQS message immediately after it is received, before processing, to ensure it is not retried.
Why wrong: Deleting immediately breaks the at-least-once processing model. If processing fails after deletion (for example, before payment is committed), the message is lost and the side effect may not be applied correctly.
- B
Implement idempotency by recording a processed marker keyed by the instruction ID and ignoring duplicates.
Idempotency ensures that repeated deliveries of the same instruction do not cause repeated side effects. By persisting a record keyed by instruction ID (or enforcing a unique constraint in a transactional store), the service can detect duplicates and safely skip or reconcile them even if SQS redelivers the message.
- C
Increase the SQS visibility timeout to a maximum value to avoid retries entirely.
Why wrong: A larger visibility timeout reduces retry frequency but does not eliminate duplicates. If the consumer times out (or crashes) after applying the side effect and before deletion, the message will still be redelivered later, so duplicates can still occur.
- D
Convert the queue to FIFO and enable content-based deduplication.
Why wrong: FIFO deduplication prevents duplicates based on message deduplication IDs at the time messages are sent to the queue. Message retries are redeliveries of the same enqueued message and are not prevented by content-based deduplication, so duplicate side effects are still possible without idempotent processing.
SAA-C03 Design Resilient Architectures Practice Question
This SAA-C03 practice question tests your understanding of design resilient architectures. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An orders service consumes payment instructions from an Amazon SQS queue. Sometimes the consumer times out after applying the payment but before deleting the SQS message. As a result, the same payment instruction is processed again. Which design change most directly prevents duplicate side effects caused by message retries?
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
Implement idempotency by recording a processed marker keyed by the instruction ID and ignoring duplicates.
Option B is correct because implementing idempotency ensures that even if the same payment instruction is processed multiple times due to a timeout and retry, the side effect (e.g., applying the payment) occurs only once. By recording a processed marker keyed by the instruction ID (e.g., using a DynamoDB table or Redis), the consumer can check the marker before processing and ignore duplicates. This directly addresses the root cause—duplicate processing—without altering the queue's retry behavior.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Delete the SQS message immediately after it is received, before processing, to ensure it is not retried.
Why it's wrong here
Deleting immediately breaks the at-least-once processing model. If processing fails after deletion (for example, before payment is committed), the message is lost and the side effect may not be applied correctly.
- ✓
Implement idempotency by recording a processed marker keyed by the instruction ID and ignoring duplicates.
Why this is correct
Idempotency ensures that repeated deliveries of the same instruction do not cause repeated side effects. By persisting a record keyed by instruction ID (or enforcing a unique constraint in a transactional store), the service can detect duplicates and safely skip or reconcile them even if SQS redelivers the message.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Increase the SQS visibility timeout to a maximum value to avoid retries entirely.
Why it's wrong here
A larger visibility timeout reduces retry frequency but does not eliminate duplicates. If the consumer times out (or crashes) after applying the side effect and before deletion, the message will still be redelivered later, so duplicates can still occur.
- ✗
Convert the queue to FIFO and enable content-based deduplication.
Why it's wrong here
FIFO deduplication prevents duplicates based on message deduplication IDs at the time messages are sent to the queue. Message retries are redeliveries of the same enqueued message and are not prevented by content-based deduplication, so duplicate side effects are still possible without idempotent processing.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse message deduplication (preventing duplicate deliveries) with idempotent processing (preventing duplicate side effects), leading them to choose Option D, which only prevents redelivery but does not handle the case where the same message is processed twice due to a consumer timeout before deletion.
Detailed technical explanation
How to think about this question
SQS at-least-once delivery guarantees that a message is delivered at least once, but can be delivered more than once due to network issues or consumer timeouts. Idempotency is a common pattern where the consumer uses a unique identifier (e.g., a payment instruction ID) to check a persistent store (e.g., DynamoDB with conditional writes) before processing; if the marker exists, the message is skipped. This approach decouples retry handling from the business logic, ensuring correctness even with multiple deliveries, and is recommended by AWS for exactly-once processing semantics in distributed systems.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this SAA-C03 question test?
Design Resilient Architectures — This question tests Design Resilient Architectures — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Implement idempotency by recording a processed marker keyed by the instruction ID and ignoring duplicates. — Option B is correct because implementing idempotency ensures that even if the same payment instruction is processed multiple times due to a timeout and retry, the side effect (e.g., applying the payment) occurs only once. By recording a processed marker keyed by the instruction ID (e.g., using a DynamoDB table or Redis), the consumer can check the marker before processing and ignore duplicates. This directly addresses the root cause—duplicate processing—without altering the queue's retry behavior.
What should I do if I get this SAA-C03 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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.
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