The answer is to configure the ALB to use a Lambda authorizer and then have that Lambda function validate the custom authorization header. This is correct because the Lambda authorizer acts as a custom authentication layer: it inspects the incoming header value, runs your validation logic, and returns an IAM policy that either allows or denies the request, which the ALB enforces before forwarding traffic to the EC2 instance. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding that while Lambda authorizers are native to API Gateway, they can also be integrated with an ALB by setting the Lambda function as a target group and using the ALB’s authentication rules. A common trap is assuming only API Gateway supports custom header validation, but the ALB’s Lambda integration handles this directly. Memory tip: think “ALB + Lambda = custom gatekeeper” — the function checks the header key, the ALB enforces the policy.
DVA-C02 Security Practice Question
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 needs to securely expose an API running on an EC2 instance behind an Application Load Balancer. The API should only be accessible to authenticated users via a custom authorization header. Which steps should be taken? (Choose TWO.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a Lambda authorizer that validates the custom header
Option A is correct because a Lambda authorizer can validate a custom authorization header by inspecting the header value and returning an IAM policy that either allows or denies access to the API. This approach is commonly used with API Gateway, but the question specifies an ALB, so the Lambda authorizer must be integrated with the ALB via a Lambda function that acts as an authenticator. The ALB can invoke a Lambda function as a target group, and the function can validate the custom header and return a response that the ALB uses to determine whether to forward the request.
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.
✓
Create a Lambda authorizer that validates the custom header
Why this is correct
Lambda authorizer can verify the token and return IAM policy.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable AWS WAF on the ALB to inspect the header
Why it's wrong here
WAF is for filtering malicious requests, not authentication.
✗
Use Amazon Cognito User Pools to validate the header
Why it's wrong here
Cognito is for user pools, not custom header validation.
✗
Use Amazon API Gateway instead of ALB
Why it's wrong here
The question specifies ALB; API Gateway is an alternative but not a step.
✓
Configure the ALB to use the Lambda authorizer
Why this is correct
ALB supports Lambda authorizers as authentication.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume API Gateway is required for Lambda authorizers, but the ALB can also invoke a Lambda function for authentication, and the question specifically asks for steps to secure the ALB, not to replace it.
Detailed technical explanation
How to think about this question
When using an ALB with a Lambda function as a target, the ALB sends the entire HTTP request to the Lambda function, which can parse the custom authorization header (e.g., 'X-Auth-Token') and return a response with a status code (e.g., 200 for allow, 403 for deny). The ALB then uses this response to decide whether to forward the request to the EC2 instance. This pattern is known as 'Lambda as a target group' and is distinct from API Gateway's Lambda authorizer, which returns an IAM policy. Under the hood, the ALB expects the Lambda to return a specific JSON structure with 'statusCode' and 'headers' to control the flow.
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.
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.
Security — This question tests Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a Lambda authorizer that validates the custom header — Option A is correct because a Lambda authorizer can validate a custom authorization header by inspecting the header value and returning an IAM policy that either allows or denies access to the API. This approach is commonly used with API Gateway, but the question specifies an ALB, so the Lambda authorizer must be integrated with the ALB via a Lambda function that acts as an authenticator. The ALB can invoke a Lambda function as a target group, and the function can validate the custom header and return a response that the ALB uses to determine whether to forward the request.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.