- A
Assume the consumer will always delete the SQS message in the same execution path, and ignore the timeout case.
Why wrong: Timeouts and crashes do occur; assuming deletion always succeeds leads directly to duplicate processing.
- B
Use idempotency: store a deterministic payment request identifier in a DynamoDB table and only create a payment when a conditional write indicates it was not processed before.
Idempotency based on a stable identifier prevents duplicates by making processing repeatable and safely detectable.
- C
Switch to SQS Standard because it provides exactly-once delivery, so duplicates cannot happen.
Why wrong: SQS Standard is at-least-once delivery; duplicates can still occur, and exactly-once is not guaranteed.
- D
Increase the consumer timeout and reduce the number of retries so that duplicates rarely occur.
Why wrong: Reducing retries lowers frequency but does not guarantee correctness; resilience requires correctness under duplicates.
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 system sends payment instructions to an Amazon SQS queue. The consumer sometimes times out after it has already created the payment record but before it deletes the SQS message. As a result, the same instruction can be processed more than once. Which design best ensures the consumer remains resilient and does not create duplicate payments when the same instruction is delivered multiple times?
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 idempotency: store a deterministic payment request identifier in a DynamoDB table and only create a payment when a conditional write indicates it was not processed before.
Option B is correct because it implements idempotency using a DynamoDB table with a conditional write. By storing a deterministic payment request identifier (e.g., a hash of the message body) and only creating the payment if the conditional write succeeds (i.e., the identifier does not already exist), the consumer can safely process the same SQS message multiple times without creating duplicate payments. This pattern ensures resilience against the at-least-once delivery semantics of SQS and consumer timeouts that prevent message deletion.
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.
- ✗
Assume the consumer will always delete the SQS message in the same execution path, and ignore the timeout case.
Why it's wrong here
Timeouts and crashes do occur; assuming deletion always succeeds leads directly to duplicate processing.
- ✓
Use idempotency: store a deterministic payment request identifier in a DynamoDB table and only create a payment when a conditional write indicates it was not processed before.
Why this is correct
Idempotency based on a stable identifier prevents duplicates by making processing repeatable and safely detectable.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Switch to SQS Standard because it provides exactly-once delivery, so duplicates cannot happen.
Why it's wrong here
SQS Standard is at-least-once delivery; duplicates can still occur, and exactly-once is not guaranteed.
- ✗
Increase the consumer timeout and reduce the number of retries so that duplicates rarely occur.
Why it's wrong here
Reducing retries lowers frequency but does not guarantee correctness; resilience requires correctness under duplicates.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume SQS FIFO queues provide exactly-once delivery, but the question specifies an SQS queue (likely Standard), and even FIFO queues only guarantee exactly-once processing within a limited deduplication window, not absolute idempotency; the correct solution is to make the consumer itself idempotent.
Detailed technical explanation
How to think about this question
DynamoDB conditional writes use the `ConditionExpression` parameter to check that an item does not already exist before writing, leveraging the table's primary key as a unique constraint. This approach is atomic and consistent, even under concurrent access, because DynamoDB ensures serializable isolation for conditional writes. In practice, the payment request identifier should be derived from idempotent fields (e.g., order ID + timestamp) to guarantee uniqueness across retries, and the DynamoDB table should be configured with on-demand capacity to handle burst retries without throttling.
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
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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: Use idempotency: store a deterministic payment request identifier in a DynamoDB table and only create a payment when a conditional write indicates it was not processed before. — Option B is correct because it implements idempotency using a DynamoDB table with a conditional write. By storing a deterministic payment request identifier (e.g., a hash of the message body) and only creating the payment if the conditional write succeeds (i.e., the identifier does not already exist), the consumer can safely process the same SQS message multiple times without creating duplicate payments. This pattern ensures resilience against the at-least-once delivery semantics of SQS and consumer timeouts that prevent message deletion.
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
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