This DVA-C02 practice question tests your understanding of security. 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 designing a serverless application using API Gateway, Lambda, and DynamoDB. The API must authenticate users using a JWT token. Which API Gateway feature should the developer use to validate the JWT before invoking the Lambda function?
Use an IAM authorizer with a resource policy.
Why wrong: IAM authorizer uses AWS SigV4, not JWT.
Use an Amazon Cognito user pool authorizer.
Why wrong: This validates Cognito tokens, but custom JWT requires a Lambda authorizer.
Use a Lambda authorizer (custom authorizer).
Lambda authorizer can validate any JWT.
Use an API Gateway resource policy to allow only authenticated IPs.
Why wrong: Resource policies do not authenticate users.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Use a Lambda authorizer (custom authorizer).
Option C is correct because a Lambda authorizer (custom authorizer) allows the developer to implement custom JWT validation logic, such as verifying the token's signature, expiry, and claims, before the request reaches the Lambda function. This is the most flexible approach when the JWT is issued by a third-party identity provider (IdP) that is not Amazon Cognito, as API Gateway's native JWT authorizer only supports JWTs from specific providers like Cognito or Auth0. The Lambda authorizer can return an IAM policy to allow or deny the request, enabling fine-grained access control based on the token's content.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Use an IAM authorizer with a resource policy.
Why it's wrong here
IAM authorizer uses AWS SigV4, not JWT.
Use an Amazon Cognito user pool authorizer.
Why it's wrong here
This validates Cognito tokens, but custom JWT requires a Lambda authorizer.
Use a Lambda authorizer (custom authorizer).
Why this is correct
Lambda authorizer can validate any JWT.
Related concept
Read the scenario before looking for a memorised answer.
Use an API Gateway resource policy to allow only authenticated IPs.
Why it's wrong here
Resource policies do not authenticate users.
Common exam traps
The trap here is that candidates often confuse the managed Cognito user pool authorizer (Option B) with the ability to validate any JWT, but the exam tests that the Cognito authorizer only works with Cognito-issued tokens, while a Lambda authorizer is required for custom or third-party JWT validation.
Detailed technical explanation
A Lambda authorizer works by receiving the JWT in the request headers (e.g., Authorization header) and executing custom code to decode and verify the token using libraries like PyJWT or jsonwebtoken. The authorizer must return an IAM policy document with Effect, Action, and Resource statements, which API Gateway caches for up to one hour by default to reduce latency. A real-world scenario is when an enterprise uses an on-premises OAuth 2.0 server or a third-party IdP like Okta; the Lambda authorizer can validate the JWT against the IdP's public keys (JWKS endpoint) and enforce custom claims like 'department' or 'role'.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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.
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FAQ
Security — This question tests Security — Read the scenario before looking for a memorised answer..
The correct answer is: Use a Lambda authorizer (custom authorizer). — Option C is correct because a Lambda authorizer (custom authorizer) allows the developer to implement custom JWT validation logic, such as verifying the token's signature, expiry, and claims, before the request reaches the Lambda function. This is the most flexible approach when the JWT is issued by a third-party identity provider (IdP) that is not Amazon Cognito, as API Gateway's native JWT authorizer only supports JWTs from specific providers like Cognito or Auth0. The Lambda authorizer can return an IAM policy to allow or deny the request, enabling fine-grained access control based on the token's content.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 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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