The answer is that the pipeline’s service role lacks the `sts:AssumeRole` permission for the cross-account role. Even when the trust policy on the target role in the prod account correctly allows the pipeline’s service role to assume it, the service role itself must have an IAM policy that explicitly grants `sts:AssumeRole` for that specific role ARN. Without this permission, the `AssumeRole` API call fails with an ‘Access Denied’ error, which is exactly the symptom described. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of the two-way permission model for cross-account role assumption: the trust policy on the target role and the permissions policy on the source role. A common trap is to check only the trust policy and overlook the source role’s permissions. Remember the mnemonic “Trust lets them in, Permissions lets you go” — both sides must be configured for the assumption to succeed.
DOP-C02 SDLC Automation Practice Question
This DOP-C02 practice question tests your understanding of sdlc automation. 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.
An organization uses AWS CodePipeline to orchestrate deployments to multiple environments (dev, test, prod). Each environment uses a different AWS account. The pipeline uses cross-account actions with IAM roles. Recently, the pipeline failed at the deploy stage for the prod account with the error 'Access Denied' when assuming the cross-account role. The role ARN is correct and the trust policy allows the pipeline's service role. What is the MOST likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The pipeline's service role lacks the `sts:AssumeRole` permission for the cross-account role.
The pipeline's service role must have an `sts:AssumeRole` permission on the cross-account role to perform the role assumption. Even if the trust policy on the cross-account role allows the pipeline's service role, the pipeline's service role itself needs an IAM policy granting `sts:AssumeRole` for the cross-account role ARN. Without this permission, the `AssumeRole` API call fails with 'Access Denied', which is the exact error described.
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.
✗
The EC2 instances in the prod account do not have an appropriate instance profile.
Why it's wrong here
The pipeline does not run on EC2 instances.
✓
The pipeline's service role lacks the `sts:AssumeRole` permission for the cross-account role.
Why this is correct
The service role needs explicit permission to assume the cross-account role.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The cross-account role's permissions boundary denies the deploy action.
Why it's wrong here
Permissions boundary affects what the role can do after assuming it, not the assumption itself.
✗
The pipeline's service role does not have permission to perform the deploy action in the prod account.
Why it's wrong here
The error occurs when assuming the role, not during the deploy action itself.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often focus on the cross-account role's trust policy or permissions, forgetting that the pipeline's service role also needs explicit `sts:AssumeRole` permission, which is a separate IAM policy requirement.
Detailed technical explanation
How to think about this question
Under the hood, CodePipeline uses the `AssumeRole` API (AWS Security Token Service) to obtain temporary credentials for the cross-account role. The pipeline's service role must have an IAM policy with `sts:AssumeRole` action on the target role ARN; the trust policy on the target role must also allow the pipeline's service role ARN as a principal. A common real-world scenario is when the pipeline's service role is created with a managed policy that does not include `sts:AssumeRole`, or the target role ARN is misspelled in the pipeline's service role policy, leading to an 'Access Denied' error even though the trust policy is correct.
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.
SDLC Automation — This question tests SDLC Automation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The pipeline's service role lacks the `sts:AssumeRole` permission for the cross-account role. — The pipeline's service role must have an `sts:AssumeRole` permission on the cross-account role to perform the role assumption. Even if the trust policy on the cross-account role allows the pipeline's service role, the pipeline's service role itself needs an IAM policy granting `sts:AssumeRole` for the cross-account role ARN. Without this permission, the `AssumeRole` API call fails with 'Access Denied', which is the exact error described.
What should I do if I get this DOP-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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 DOP-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 DOP-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.