The correct answer is to use the organization policy constraint `compute.restrictServiceAccountUsage`. This constraint enforces service account usage on Compute Engine by allowing you to define an explicit allowlist of service accounts (by email or ID) at the organization, folder, or project level; any attempt to launch an instance with a service account not on that list is denied by Resource Manager, directly implementing the policy that only specific service accounts are permitted. On the Google Professional Cloud Security Engineer exam, this question tests your understanding of how organization policy constraints govern resource creation, and a common trap is confusing this with IAM roles or the `iam.serviceAccountUser` role, which control who can *use* a service account rather than which service accounts can be *attached* to an instance. A helpful memory tip: think of the constraint name as “restrict the service account that gets used on the compute instance” — it’s a whitelist for the instance’s identity, not for the user’s permissions.
PCSE Practice Question: Configuring access within a cloud solution environment
This PCSE practice question tests your understanding of configuring access within a cloud solution environment. 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 company has a policy that only specific service accounts can be used on Compute Engine instances. How can this be enforced?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use an organization policy with constraint compute.restrictServiceAccountUsage.
Option D is correct because the organization policy constraint `compute.restrictServiceAccountUsage` is specifically designed to enforce which service accounts can be used when creating Compute Engine instances. When applied at the project, folder, or organization level, this constraint allows you to define a list of allowed service accounts (by email or ID), and any attempt to launch an instance with a service account not on that list will be denied by the Resource Manager. This directly enforces the company policy that only specific service accounts are permitted on Compute Engine instances.
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 IAM conditions on the compute.instanceAdmin role to restrict the service account.
Why it's wrong here
While possible, this is not as straightforward or enforceable as an organization policy.
✗
Use Identity-Aware Proxy (IAP).
Why it's wrong here
IAP controls access to applications, not service account usage.
✗
Use a VPC Service Controls perimeter.
Why it's wrong here
VPC Service Controls restrict data exfiltration, not service account usage.
✓
Use an organization policy with constraint compute.restrictServiceAccountUsage.
Why this is correct
This constraint restricts which service accounts can be attached to Compute Engine instances.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the distinction between IAM roles (who can perform actions) and organization policy constraints (what configurations are allowed), so candidates mistakenly choose IAM conditions (Option A) thinking they can filter service accounts, when in reality only the organization policy constraint can enforce a whitelist of permitted service accounts on Compute Engine instances.
Detailed technical explanation
How to think about this question
The `compute.restrictServiceAccountUsage` constraint is a list-based organization policy that accepts service account email addresses (e.g., `sa@project.iam.gserviceaccount.com`) or the special value `projects/PROJECT_ID/serviceAccounts/SERVICE_ACCOUNT_ID`. When enforced, the Compute Engine API checks the instance's `serviceAccounts` field against the allowed list during instance creation; if the service account is not in the list, the request fails with a `403` error. This constraint can be combined with `iam.workloadIdentityPoolProviders` to further restrict which external identities can assume the allowed service accounts, providing a defense-in-depth approach for workload identity management.
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.
Configuring access within a cloud solution environment — This question tests Configuring access within a cloud solution environment — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use an organization policy with constraint compute.restrictServiceAccountUsage. — Option D is correct because the organization policy constraint `compute.restrictServiceAccountUsage` is specifically designed to enforce which service accounts can be used when creating Compute Engine instances. When applied at the project, folder, or organization level, this constraint allows you to define a list of allowed service accounts (by email or ID), and any attempt to launch an instance with a service account not on that list will be denied by the Resource Manager. This directly enforces the company policy that only specific service accounts are permitted on Compute Engine instances.
What should I do if I get this PCSE 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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