DVA-C02 Troubleshooting and Optimization Practice Question
A developer has deployed a serverless application using AWS SAM. After a recent update, the API Gateway endpoints return 500 errors. The Lambda function logs show no errors. What should the developer investigate first?
⚠ Common exam trap
Test-takers frequently assume 500 errors always originate from the Lambda function, but the question explicitly states Lambda logs show no errors, forcing the candidate to look at the API Gateway integration layer instead.
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
✓
Verify the API Gateway integration response and mapping templates.
When API Gateway returns 500 errors but Lambda logs show no errors, the issue is typically in the API Gateway integration response or mapping templates. API Gateway may fail to transform the Lambda response into the expected format, causing an internal server error without the Lambda function ever throwing an exception.
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 timeout.
Why it's wrong here
Increasing the Lambda function timeout would only be relevant if the function was consistently exceeding its execution duration, resulting in a 504 Gateway Timeout from API Gateway or a specific Lambda timeout error in CloudWatch Logs. Since the Lambda function is reported to be executing successfully, a timeout is not the root cause of the 500 Internal Server Error originating from API Gateway.
- ✗
Check the Lambda function's reserved concurrency.
Why it's wrong here
If a Lambda function reaches its reserved concurrency limit, subsequent invocation requests are throttled by AWS Lambda. API Gateway translates these throttling errors into a 429 Too Many Requests HTTP status code for the client, not a 500 Internal Server Error. Therefore, checking reserved concurrency is not relevant when API Gateway returns a 500 error after a successful Lambda execution.
- ✗
Review the CloudFormation stack events for any failures.
Why it's wrong here
CloudFormation stack events primarily detail the lifecycle and status of resource provisioning and updates within a stack. While deployment failures could prevent the application from functioning, they do not typically cause a runtime 500 Internal Server Error from API Gateway when the underlying Lambda function is successfully invoked. Runtime issues, such as incorrect data transformations, are not reflected in CloudFormation deployment logs.
- ✓
Verify the API Gateway integration response and mapping templates.
Why this is correct
Even if a Lambda function executes successfully and returns a valid response, API Gateway can still return a 500 Internal Server Error to the client if its integration response or mapping templates are misconfigured. These templates are responsible for transforming the Lambda function's output into the final HTTP response format expected by the client. A failure in this transformation process within API Gateway itself often manifests as a 500 error.
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 |
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.