Google PCA Manage implementation of cloud architecture Practice Question
This PCA practice question tests your understanding of manage implementation of cloud architecture. 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.
Exhibit
Refer to the exhibit.
error: googleapi: Error 403: The caller does not have permission, forbidden
Stackdriver Logging logged: 'iam.serviceAccounts.actAs' permission on service account '12345-compute@developer.gserviceaccount.com'.
A developer is trying to deploy a Compute Engine instance from a Cloud Build step. The build fails with the above error. What is the problem?
Refer to the exhibit.
error: googleapi: Error 403: The caller does not have permission, forbidden
Stackdriver Logging logged: 'iam.serviceAccounts.actAs' permission on service account '12345-compute@developer.gserviceaccount.com'.
A
The project has exceeded its service account quota.
Why wrong: No quota error.
B
The Cloud Build service account lacks 'compute.instances.create' permission.
Why wrong: Error says actAs, not create.
C
Cloud Build does not have the 'iam.serviceAccounts.actAs' permission on the default compute service account.
When Cloud Build creates a VM, it must act as the VM's service account.
D
The developer's personal account does not have permission to use Cloud Build.
Why wrong: Error from Cloud Build service account.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Cloud Build does not have the 'iam.serviceAccounts.actAs' permission on the default compute service account.
The error occurs because Cloud Build needs to impersonate the Compute Engine default service account to create a VM instance. The Cloud Build service account requires the 'iam.serviceAccounts.actAs' permission on the target service account to delegate its identity. Without this permission, the build step fails even if the Cloud Build service account has 'compute.instances.create' permission.
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 project has exceeded its service account quota.
Why it's wrong here
No quota error.
✗
The Cloud Build service account lacks 'compute.instances.create' permission.
Why it's wrong here
Error says actAs, not create.
✓
Cloud Build does not have the 'iam.serviceAccounts.actAs' permission on the default compute service account.
Why this is correct
When Cloud Build creates a VM, it must act as the VM's service account.
Related concept
Read the scenario before looking for a memorised answer.
✗
The developer's personal account does not have permission to use Cloud Build.
Why it's wrong here
Error from Cloud Build service account.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the subtle distinction between having resource-level permissions (like 'compute.instances.create') and the 'actAs' permission required to impersonate a service account, leading candidates to incorrectly choose the missing resource permission.
Detailed technical explanation
How to think about this question
The 'iam.serviceAccounts.actAs' permission is required for Cloud Build to use the service account's identity when calling Google Cloud APIs on behalf of the build. This is enforced via the IAM condition that checks whether the caller (Cloud Build) has the 'actAs' role on the target service account. In practice, this permission is often granted by assigning the 'roles/iam.serviceAccountUser' role to the Cloud Build service account on the default compute service account.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this PCA question in full detail.
Manage implementation of cloud architecture — This question tests Manage implementation of cloud architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Cloud Build does not have the 'iam.serviceAccounts.actAs' permission on the default compute service account. — The error occurs because Cloud Build needs to impersonate the Compute Engine default service account to create a VM instance. The Cloud Build service account requires the 'iam.serviceAccounts.actAs' permission on the target service account to delegate its identity. Without this permission, the build step fails even if the Cloud Build service account has 'compute.instances.create' permission.
What should I do if I get this PCA 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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Question Discussion
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