- A
Enable Lambda function's batch window to 0.
Why wrong: Batch window does not affect ordering.
- B
Configure the Lambda event source mapping to use the FIFO queue.
The event source mapping must be configured to read from the FIFO queue.
- C
Use a standard SQS queue.
Why wrong: Standard queues do not guarantee ordering or exactly-once.
- D
Set the Lambda function's reserved concurrency to 1.
Reserved concurrency of 1 prevents parallel processing, preserving order.
- E
Use a FIFO SQS queue with a message deduplication ID.
FIFO queues guarantee order and exactly-once with deduplication.
Question 1,243 of 1,746
SAP-C02 FIFO Queue Practice Question
This SAP-C02 practice question tests your understanding of continuous improvement for existing solutions. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. A key principle to apply: fIFO Queue. 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 serverless event-driven application using AWS Lambda. The application processes messages from an Amazon SQS queue. The team needs to ensure that messages are processed in order and exactly once. Which THREE steps should be taken?
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
✓
Configure the Lambda event source mapping to use the FIFO queue.
To achieve message ordering and exactly-once processing with Lambda and SQS, you must use a FIFO queue (option B) because FIFO queues preserve the order of messages. Additionally, enable the queue's content-based deduplication or provide a deduplication ID (option E) to prevent duplicate messages from being processed. Finally, set the Lambda function's reserved concurrency to 1 (option D) to ensure that only one instance of the function processes messages at a time, maintaining the order. Option A (batch window 0) is incorrect because it would cause Lambda to wait longer, but does not help with ordering. Option C (standard queue) does not guarantee ordering or deduplication.
Key principle: FIFO Queue
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable Lambda function's batch window to 0.
Why it's wrong here
Batch window does not affect ordering.
- ✓
Configure the Lambda event source mapping to use the FIFO queue.
Why this is correct
The event source mapping must be configured to read from the FIFO queue.
Related concept
FIFO Queue
- ✗
Use a standard SQS queue.
Why it's wrong here
Standard queues do not guarantee ordering or exactly-once.
- ✓
Set the Lambda function's reserved concurrency to 1.
Why this is correct
Reserved concurrency of 1 prevents parallel processing, preserving order.
Related concept
FIFO Queue
- ✓
Use a FIFO SQS queue with a message deduplication ID.
Why this is correct
FIFO queues guarantee order and exactly-once with deduplication.
Related concept
FIFO Queue
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
Treat this as a scenario question. Identify the problem, the constraint, and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- FIFO Queue
- Message Deduplication
- Reserved Concurrency
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
FIFO Queue
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.
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
What to study next
Got this wrong? Here's your next step.
Review fIFO Queue, then practise related SAP-C02 questions on the same topic to reinforce the concept.
- →
Continuous Improvement for Existing Solutions — study guide chapter
Learn the concepts, then practise the questions
- →
Continuous Improvement for Existing Solutions practice questions
Targeted practice on this topic area only
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FAQ
Questions learners often ask
What does this SAP-C02 question test?
Continuous Improvement for Existing Solutions — This question tests Continuous Improvement for Existing Solutions — FIFO Queue.
What is the correct answer to this question?
The correct answer is: Configure the Lambda event source mapping to use the FIFO queue. — To achieve message ordering and exactly-once processing with Lambda and SQS, you must use a FIFO queue (option B) because FIFO queues preserve the order of messages. Additionally, enable the queue's content-based deduplication or provide a deduplication ID (option E) to prevent duplicate messages from being processed. Finally, set the Lambda function's reserved concurrency to 1 (option D) to ensure that only one instance of the function processes messages at a time, maintaining the order. Option A (batch window 0) is incorrect because it would cause Lambda to wait longer, but does not help with ordering. Option C (standard queue) does not guarantee ordering or deduplication.
What should I do if I get this SAP-C02 question wrong?
Review fIFO Queue, then practise related SAP-C02 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
FIFO Queue
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Last reviewed: Jun 20, 2026
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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