Why Is My Lambda Returning 200 But Application Not Working?
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.
Network Topology
Refer to the exhibit. A developer runs the AWS CLI command to invoke a Lambda function. The output shows StatusCode 200 and no FunctionError. However, the application that depends on this function's output is not working correctly. What should the developer check next?
Network Topology
A
Check the Lambda function's CloudWatch Logs for any errors or unexpected output.
CloudWatch Logs contain the function's output and any debug information.
B
Check the IAM role attached to the Lambda function for insufficient permissions.
Why wrong: Permission errors would also appear in logs and might cause FunctionError.
C
Check the payload format against the function's expected input.
Why wrong: While payload format could be wrong, the function ran successfully; logs would show if parsing fails.
D
Check the Lambda function's memory and timeout configuration.
Why wrong: Memory/timeout issues would likely cause a FunctionError.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Check the Lambda function's CloudWatch Logs for any errors or unexpected output.
A StatusCode 200 with no FunctionError indicates the Lambda function executed without a runtime or invocation error. However, the application may still fail if the function returns incorrect data, throws an unhandled exception, or produces unexpected output. Checking CloudWatch Logs is the first step to see the actual logs, error messages, or return values that would reveal logic errors or misconfigurations.
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.
✓
Check the Lambda function's CloudWatch Logs for any errors or unexpected output.
Why this is correct
CloudWatch Logs contain the function's output and any debug information.
Related concept
Read the scenario before looking for a memorised answer.
✗
Check the IAM role attached to the Lambda function for insufficient permissions.
Why it's wrong here
Permission errors would also appear in logs and might cause FunctionError.
✗
Check the payload format against the function's expected input.
Why it's wrong here
While payload format could be wrong, the function ran successfully; logs would show if parsing fails.
✗
Check the Lambda function's memory and timeout configuration.
Why it's wrong here
Memory/timeout issues would likely cause a FunctionError.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume a 200 status code guarantees correct application behavior, but Lambda's success response only indicates the function ran, not that its output is valid for the caller.
Trap categories for this question
Command / output trap
While payload format could be wrong, the function ran successfully; logs would show if parsing fails.
Detailed technical explanation
How to think about this question
Lambda invocation returns a 200 status code as long as the function handler runs to completion without throwing an unhandled exception. However, the function could still return a malformed response (e.g., wrong data type, missing fields) that the downstream application cannot parse. CloudWatch Logs capture all console.log output and any errors, making them essential for debugging logic issues that don't surface as invocation 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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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.
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: Check the Lambda function's CloudWatch Logs for any errors or unexpected output. — A StatusCode 200 with no FunctionError indicates the Lambda function executed without a runtime or invocation error. However, the application may still fail if the function returns incorrect data, throws an unhandled exception, or produces unexpected output. Checking CloudWatch Logs is the first step to see the actual logs, error messages, or return values that would reveal logic errors or misconfigurations.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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