- A
Increase the Lambda function memory allocation.
Why wrong: Memory increase improves performance but does not resolve concurrency throttling.
- B
Increase the Lambda function timeout.
Why wrong: Lambda timeout errors produce 504, not 503.
- C
Request a service quota increase for Lambda concurrent executions.
Lambda concurrent execution limits cause 503 errors when exceeded.
- D
Increase the API Gateway throttling limits.
Why wrong: API Gateway throttling causes 429 errors, not 503.
Question 267 of 1,616
Troubleshooting Intermittent 503 Errors from API Gateway: Lambda Concurrency
This DVA-C02 practice question tests your understanding of development with aws services. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 using AWS Lambda functions behind an Amazon API Gateway REST API. Users report intermittent 503 errors. The Lambda function code appears correct. Which action is MOST likely to resolve the issue?
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
✓
Request a service quota increase for Lambda concurrent executions.
Option C is correct because intermittent 503 errors from API Gateway often indicate that Lambda concurrent execution limits have been reached. When the number of simultaneous invocations exceeds the account-level or function-level reserved concurrency, API Gateway returns a 503 'Service Unavailable' response. Increasing the Lambda concurrent executions quota allows more invocations to be processed without throttling.
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.
- ✗
Increase the Lambda function memory allocation.
Why it's wrong here
Memory increase improves performance but does not resolve concurrency throttling.
- ✗
Increase the Lambda function timeout.
Why it's wrong here
Lambda timeout errors produce 504, not 503.
- ✓
Request a service quota increase for Lambda concurrent executions.
Why this is correct
Lambda concurrent execution limits cause 503 errors when exceeded.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Increase the API Gateway throttling limits.
Why it's wrong here
API Gateway throttling causes 429 errors, not 503.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse API Gateway throttling limits (which return 429 errors) with Lambda concurrency limits (which return 503 errors), leading them to incorrectly choose option D.
Detailed technical explanation
How to think about this question
Lambda has a default account-level concurrent execution limit of 1,000 (can be increased via quota request). When this limit is hit, subsequent invocations receive a 429 or 503 error depending on the integration. API Gateway's integration with Lambda uses synchronous invocation, so it directly exposes Lambda's throttling behavior. A common real-world scenario is a sudden traffic spike overwhelming the default concurrency, causing intermittent failures that appear as 503 errors.
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 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.
Visual reference
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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Development with AWS Services — study guide chapter
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FAQ
Questions learners often ask
What does this DVA-C02 question test?
Development with AWS Services — This question tests Development with AWS Services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Request a service quota increase for Lambda concurrent executions. — Option C is correct because intermittent 503 errors from API Gateway often indicate that Lambda concurrent execution limits have been reached. When the number of simultaneous invocations exceeds the account-level or function-level reserved concurrency, API Gateway returns a 503 'Service Unavailable' response. Increasing the Lambda concurrent executions quota allows more invocations to be processed without throttling.
What should I do if I get this DVA-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 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.
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