- A
The function memory is too low.
Why wrong: Memory affects speed but not throttling errors.
- B
The reserved concurrency is too low.
Low reserved concurrency causes throttling (429) and delays leading to timeouts.
- C
The SQS batch size is too large.
Why wrong: Batch size affects processing but not throttling.
- D
The function timeout is too low.
Why wrong: Timeout is 30s, but function fails at 15s due to throttling.
Question 1,364 of 1,616
DVA-C02 Reserved concurrency Practice Question
This DVA-C02 practice question tests your understanding of troubleshooting and optimization. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. A key principle to apply: reserved concurrency. 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 developer deployed a new Lambda function that processes messages from an SQS queue. The function runs correctly for small workloads but starts timing out after 15 seconds when traffic increases. The function has a reserved concurrency of 10 and a timeout of 30 seconds. CloudWatch logs show occasional throttling errors (429). What is the MOST likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
✓
The reserved concurrency is too low.
The correct answer is B. When traffic increases, the Lambda function experiences throttling errors (429) because the reserved concurrency of 10 is too low to handle the surge of concurrent invocations from SQS. Although the function timeout is set to 30 seconds, throttling causes requests to be queued, and by the time they are processed, they may exceed the Lambda timeout (15 seconds observed) and fail. Option A is incorrect because memory affects execution speed, not concurrency limits. Option C is incorrect because SQS batch size determines messages per invocation, but throttling is about concurrency, not batch size. Option D is incorrect because the timeout is already 30 seconds; the timeouts are a consequence of throttling, not an insufficient timeout value.
Key principle: Reserved concurrency
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The function memory is too low.
Why it's wrong here
Memory affects speed but not throttling errors.
- ✓
The reserved concurrency is too low.
Why this is correct
Low reserved concurrency causes throttling (429) and delays leading to timeouts.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Reserved concurrency
- ✗
The SQS batch size is too large.
Why it's wrong here
Batch size affects processing but not throttling.
- ✗
The function timeout is too low.
Why it's wrong here
Timeout is 30s, but function fails at 15s due to throttling.
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
- Reserved concurrency
- Throttling (429 error)
- Lambda-SQS integration
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
Reserved concurrency
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 reserved concurrency, then practise related DVA-C02 questions on the same topic to reinforce the concept.
- →
Troubleshooting and Optimization — study guide chapter
Learn the concepts, then practise the questions
- →
Troubleshooting and Optimization practice questions
Targeted practice on this topic area only
- →
All DVA-C02 questions
1,616 questions across all exam domains
- →
AWS Certified Developer Associate DVA-C02 study guide
Full concept coverage aligned to exam objectives
- →
DVA-C02 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related DVA-C02 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Development with AWS Services practice questions
Practise DVA-C02 questions linked to Development with AWS Services.
Security practice questions
Practise DVA-C02 questions linked to Security.
Deployment practice questions
Practise DVA-C02 questions linked to Deployment.
Troubleshooting and Optimization practice questions
Practise DVA-C02 questions linked to Troubleshooting and Optimization.
DVA-C02 fundamentals practice questions
Practise DVA-C02 questions linked to DVA-C02 fundamentals.
DVA-C02 scenario practice questions
Practise DVA-C02 questions linked to DVA-C02 scenario.
DVA-C02 troubleshooting practice questions
Practise DVA-C02 questions linked to DVA-C02 troubleshooting.
Practice this exam
Start a free DVA-C02 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this DVA-C02 question test?
Troubleshooting and Optimization — This question tests Troubleshooting and Optimization — Reserved concurrency.
What is the correct answer to this question?
The correct answer is: The reserved concurrency is too low. — The correct answer is B. When traffic increases, the Lambda function experiences throttling errors (429) because the reserved concurrency of 10 is too low to handle the surge of concurrent invocations from SQS. Although the function timeout is set to 30 seconds, throttling causes requests to be queued, and by the time they are processed, they may exceed the Lambda timeout (15 seconds observed) and fail. Option A is incorrect because memory affects execution speed, not concurrency limits. Option C is incorrect because SQS batch size determines messages per invocation, but throttling is about concurrency, not batch size. Option D is incorrect because the timeout is already 30 seconds; the timeouts are a consequence of throttling, not an insufficient timeout value.
What should I do if I get this DVA-C02 question wrong?
Review reserved concurrency, then practise related DVA-C02 questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Reserved concurrency
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 →
Keep practising
More DVA-C02 practice questions
- A developer is troubleshooting an AWS Lambda function that is triggered by an S3 event. The function occasionally fails…
- A developer needs to call AWS APIs from application code running on EC2. Which credential source should the AWS SDK use…
- A developer needs to allow an IAM user in a different AWS account to assume a role in the developer's account. The role…
- A developer needs to grant an IAM role in Account B read-only access to objects in an S3 bucket in Account A. The bucket…
- An API Gateway HTTP API should allow access only to users authenticated by an external OIDC provider. Which authorizer t…
- A developer needs to allow an EC2 instance to read from a DynamoDB table. Which is the best practice to grant permission…
Last reviewed: Jun 20, 2026
This DVA-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 DVA-C02 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.