DVA-C02 Development with AWS Services Practice Question
This DVA-C02 practice question tests your understanding of development with aws services. 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. 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 developer is building a serverless API using Amazon API Gateway and AWS Lambda. The API accepts JSON payloads in the request body. The developer wants to ensure that incoming requests have a valid structure before being passed to the Lambda function to reduce unnecessary invocations. Which API Gateway feature should the developer use?
Request validation using models and request validators
API Gateway request validation checks the request against a model (JSON schema). It rejects invalid requests before reaching the integration, reducing Lambda invocations.
B
Usage plans with API keys
Why wrong: Usage plans control throttling and quota limits per API key, but they do not validate request payload structure.
C
WAF (AWS WAF) integration
Why wrong: AWS WAF protects against web exploits and bot traffic but does not validate JSON schemas in request bodies.
D
Custom authorizer (Lambda authorizer)
Why wrong: Custom authorizers validate authentication tokens, not the request body payload structure.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Request validation using models and request validators
Option A is correct because API Gateway's request validation feature allows you to define a JSON Schema model for the request body and attach a request validator to the method. This validates the payload structure before the request reaches the Lambda function, preventing invalid payloads from triggering unnecessary invocations and reducing costs.
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.
✓
Request validation using models and request validators
Why this is correct
API Gateway request validation checks the request against a model (JSON schema). It rejects invalid requests before reaching the integration, reducing Lambda invocations.
Related concept
Read the scenario before looking for a memorised answer.
✗
Usage plans with API keys
Why it's wrong here
Usage plans control throttling and quota limits per API key, but they do not validate request payload structure.
✗
WAF (AWS WAF) integration
Why it's wrong here
AWS WAF protects against web exploits and bot traffic but does not validate JSON schemas in request bodies.
✗
Custom authorizer (Lambda authorizer)
Why it's wrong here
Custom authorizers validate authentication tokens, not the request body payload structure.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse request validation (payload structure checking) with authorization (who can call the API) or security filtering (WAF), leading them to pick a wrong option like custom authorizer or WAF integration.
Detailed technical explanation
How to think about this question
Under the hood, API Gateway request validation uses a JSON Schema draft-04 model defined in the API Gateway REST API's Models section. The request validator compares the incoming request body against the model and returns a 400 Bad Request response with validation errors if the payload does not conform, all without invoking the backend Lambda. In a real-world scenario, this is critical for high-traffic APIs where invalid payloads could otherwise cause excessive Lambda cold starts and cost spikes.
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.
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: Request validation using models and request validators — Option A is correct because API Gateway's request validation feature allows you to define a JSON Schema model for the request body and attach a request validator to the method. This validates the payload structure before the request reaches the Lambda function, preventing invalid payloads from triggering unnecessary invocations and reducing costs.
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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