The answer is to use an SQS FIFO queue with content-based deduplication enabled. This configuration is correct because FIFO queues inherently guarantee exactly-once processing by preventing duplicate message delivery through a strict first-in-first-out order and a deduplication ID that the queue uses to identify and discard any retried or resent messages within a five-minute deduplication interval. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of how to achieve exactly-once semantics in a serverless architecture, often appearing as a trap where candidates mistakenly choose a standard SQS queue or Lambda destinations—but standard queues only offer at-least-once delivery, and Lambda destinations handle execution results, not message deduplication. A key memory tip is to think “FIFO for finality”: FIFO queues are the only SQS type that enforces exactly-once processing, making them the go-to choice when your application cannot tolerate duplicates.
SAP-C02 Design for New Solutions Practice Question
This SAP-C02 practice question tests your understanding of design for new solutions. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
A company is designing a new serverless application on AWS. The application consists of multiple AWS Lambda functions that process incoming events from an Amazon SQS queue. The company wants to ensure that each message is processed exactly once. Which configuration should the company use?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use an SQS FIFO queue and enable content-based deduplication.
Option B is correct because SQS FIFO queues guarantee exactly-once processing. Option A is wrong because standard SQS queues do not guarantee exactly-once. Option C is wrong because Lambda destination is for success/failure, not exactly-once. Option D is wrong because DynamoDB Streams are not for SQS.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 a standard SQS queue and set the Lambda function reserved concurrency to 1.
Why it's wrong here
Standard SQS queues offer at-least-once delivery, not exactly-once.
✓
Use an SQS FIFO queue and enable content-based deduplication.
Why this is correct
SQS FIFO queues support exactly-once processing when combined with deduplication IDs.
Related concept
Static NAT maps one inside address to one outside address.
✗
Use a standard SQS queue and configure Lambda destinations for the queue.
Why it's wrong here
Lambda destinations handle async invocation results, not exactly-once processing.
✗
Use an SQS FIFO queue and configure DynamoDB Streams as the event source for Lambda.
Why it's wrong here
SQS FIFO can directly trigger Lambda; DynamoDB Streams are not needed.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related SAP-C02 NAT questions on configuration and troubleshooting.
Design for New Solutions — This question tests Design for New Solutions — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Use an SQS FIFO queue and enable content-based deduplication. — Option B is correct because SQS FIFO queues guarantee exactly-once processing. Option A is wrong because standard SQS queues do not guarantee exactly-once. Option C is wrong because Lambda destination is for success/failure, not exactly-once. Option D is wrong because DynamoDB Streams are not for SQS.
What should I do if I get this SAP-C02 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related SAP-C02 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is designing a new microservices application on AWS. The application consists of several services that need to communicate asynchronously. One service generates orders and sends them to a processing service. The order volume can vary significantly, and the processing service must scale independently. The company wants to use a managed service to decouple the services and ensure that messages are not lost. The processing service is written in Python and runs on AWS Lambda. The solutions architect needs to design the message delivery mechanism. The architect decides to use Amazon SQS. However, the Lambda function sometimes fails to process a message due to a transient error, and the message should be retried. After a maximum of three retries, the message should be moved to a dead-letter queue for analysis. Which configuration should the architect use?
medium
A.Configure the SQS DLQ with a redrive policy that allows messages to be sent back to the source queue after 3 retries.
✓ B.Configure the SQS queue with a visibility timeout of 6 minutes and a redrive policy with maxReceiveCount of 3, pointing to a DLQ.
C.Configure the SQS queue with a visibility timeout of 30 seconds and a redrive policy with maxReceiveCount of 3, pointing to a DLQ.
D.Configure Lambda with a reserved concurrency of 1 and set the SQS queue's redrive policy to maxReceiveCount of 3.
Why B: Amazon SQS supports redrive policy with maxReceiveCount to specify the number of retries before moving to a DLQ. Setting maxReceiveCount to 3 and specifying a DLQ ARN meets the requirement. Option B is correct. Option A is wrong because setting the visibility timeout too high delays retries. Option C is wrong because Lambda's retry behavior is separate; SQS handles retries via visibility timeout. Option D is wrong because DLQ must be configured on the source queue, not the DLQ itself.
Last reviewed: Jun 20, 2026
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This SAP-C02 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 SAP-C02 exam.
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