- A
Use a VPC Link to connect to a private server for validation.
Why wrong: VPC Link is for private integration, not token validation.
- B
Validate the token inside the Lambda function integrated with the API.
Why wrong: This adds latency as the token is validated after invocation.
- C
Use API Gateway request validation to check the header format.
Why wrong: Request validation only checks format and presence, not token validity.
- D
Use a Lambda authorizer (formerly custom authorizer) on the API Gateway.
Lambda authorizer caches the policy, minimizing latency for subsequent requests.
Question 328 of 1,616
Low Latency JWT Validation Using Lambda Authorizer
This DVA-C02 practice question tests your understanding of development with aws services. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 REST API using Amazon API Gateway with a Lambda integration. The API must validate that the 'Authorization' header contains a valid JWT token before invoking the backend. Which approach provides the LOWEST latency for token validation?
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
✓
Use a Lambda authorizer (formerly custom authorizer) on the API Gateway.
Option D is correct because a Lambda authorizer (formerly custom authorizer) runs before the backend Lambda invocation, caching the JWT validation result for a configurable TTL (default 300 seconds). This avoids re-validating the token on every request, providing the lowest latency for token validation compared to validating inside the backend Lambda.
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.
- ✗
Use a VPC Link to connect to a private server for validation.
Why it's wrong here
VPC Link is for private integration, not token validation.
- ✗
Validate the token inside the Lambda function integrated with the API.
Why it's wrong here
This adds latency as the token is validated after invocation.
- ✗
Use API Gateway request validation to check the header format.
Why it's wrong here
Request validation only checks format and presence, not token validity.
- ✓
Use a Lambda authorizer (formerly custom authorizer) on the API Gateway.
Why this is correct
Lambda authorizer caches the policy, minimizing latency for subsequent requests.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
It is a common misconception that API Gateway request validation can handle JWT token validation, but it only validates structural format (e.g., header presence), not cryptographic signature verification.
Detailed technical explanation
How to think about this question
Lambda authorizers can return an IAM policy that is cached by API Gateway, meaning subsequent requests with the same token within the TTL bypass the authorizer invocation entirely. The authorizer itself can use libraries like PyJWT or jsonwebtoken to verify the token's signature against the issuer's JWKS endpoint, and the cached policy is stored in API Gateway's in-memory cache for sub-millisecond retrieval.
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
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
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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: Use a Lambda authorizer (formerly custom authorizer) on the API Gateway. — Option D is correct because a Lambda authorizer (formerly custom authorizer) runs before the backend Lambda invocation, caching the JWT validation result for a configurable TTL (default 300 seconds). This avoids re-validating the token on every request, providing the lowest latency for token validation compared to validating inside the backend Lambda.
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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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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