The answer is that the IAM policy must be attached to the CodePipeline service role, not to the developer’s IAM user. This is because CodePipeline operates using a service role to assume permissions for triggering downstream actions like CodeBuild; when the policy is attached to the user, the pipeline itself lacks the required `codebuild:StartBuild` authorization, resulting in the AccessDenied error even though the policy’s resource is set to `*`. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding of how service roles decouple user permissions from automated service actions—a common trap is assuming that granting permissions to a developer’s account will propagate to the CI/CD pipeline. Remember the memory tip: “Pipelines need their own role, not your own goal.”
DVA-C02 Deployment Practice Question
This DVA-C02 practice question tests your understanding of deployment. 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.
Refer to the exhibit. A developer created this IAM policy to allow a CI/CD service to trigger CodePipeline and CodeBuild. However, the pipeline fails with an 'AccessDenied' error when trying to start the CodeBuild project. What is the likely cause?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The policy is attached to the developer's IAM user instead of the CodePipeline service role.
Option B is correct because the policy allows 'codebuild:StartBuild' on all resources, but CodePipeline needs to start builds on behalf of the pipeline. The CodeBuild project resource ARN is not specified; however, the 'Resource' is '*', so that should be fine. Actually, the issue might be that the policy allows StartBuild for CodeBuild, but the pipeline's service role needs permissions. The policy shown is for a user, not for the pipeline's service role. The question says 'a developer created this IAM policy', but the pipeline uses a service role. So the correct answer is that the policy should be attached to the pipeline's service role, not the developer. Option A is wrong because the action is correct. Option C is wrong because the resource is '*', covering all projects. Option D is wrong because the policy does not need to be attached to the user; it needs to be attached to the pipeline's role.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The policy should use 'Effect': 'Deny' for the CodeBuild actions.
Why it's wrong here
Denying would cause access denied, but the policy is Allow.
✗
The policy does not include 'codebuild:StartBuild' for the specific CodeBuild project ARN.
Why it's wrong here
The policy uses 'Resource': '*', which covers all projects, so this is not the issue.
✗
The policy must include 'codebuild:BatchGetBuilds' for the specific project.
Why it's wrong here
The policy already includes BatchGetBuilds with '*' resource.
✓
The policy is attached to the developer's IAM user instead of the CodePipeline service role.
Why this is correct
CodePipeline uses a service role to perform actions; the policy must be attached to that role.
Related concept
Standard ACLs match source addresses.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DVA-C02 ACL questions on filtering logic and placement.
Deployment — This question tests Deployment — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: The policy is attached to the developer's IAM user instead of the CodePipeline service role. — Option B is correct because the policy allows 'codebuild:StartBuild' on all resources, but CodePipeline needs to start builds on behalf of the pipeline. The CodeBuild project resource ARN is not specified; however, the 'Resource' is '*', so that should be fine. Actually, the issue might be that the policy allows StartBuild for CodeBuild, but the pipeline's service role needs permissions. The policy shown is for a user, not for the pipeline's service role. The question says 'a developer created this IAM policy', but the pipeline uses a service role. So the correct answer is that the policy should be attached to the pipeline's service role, not the developer. Option A is wrong because the action is correct. Option C is wrong because the resource is '*', covering all projects. Option D is wrong because the policy does not need to be attached to the user; it needs to be attached to the pipeline's role.
What should I do if I get this DVA-C02 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DVA-C02 ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
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