- A
A user must have the roles/iam.serviceAccountUser role on the service account to impersonate it.
Why wrong: Incorrect. The roles/iam.serviceAccountUser role allows a user to list service accounts and get their metadata, but not to impersonate them. Impersonation requires the roles/iam.serviceAccountTokenCreator role or the specific iam.serviceAccounts.getAccessToken permission.
- B
The Security Token Service (sts.googleapis.com) must be enabled for impersonation.
Why wrong: Incorrect. While the Security Token Service (STS) is used to exchange tokens, enabling sts.googleapis.com is not required for service account impersonation. Impersonation uses the IAM API and the service account's credentials directly.
- C
Impersonation requires the iam.serviceAccounts.getAccessToken permission.
Correct. The iam.serviceAccounts.getAccessToken permission is required to generate an access token for a service account, which is the core mechanism of impersonation.
- D
Service accounts cannot impersonate other service accounts.
Why wrong: Incorrect. Service accounts can impersonate other service accounts if they have the appropriate permissions. This is commonly used for cross-project access.
- E
Impersonation can be used to delegate access across projects.
Correct. Impersonation allows a user or service account to act as another service account, enabling delegated access across projects.
Service Account Impersonation: What Permissions Are Actually Required?
This PCSE practice question tests your understanding of pcse exam topics. 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.
A security engineer is configuring service account impersonation for cross-project access. Which two statements about service account impersonation are true? (Choose two.)
Quick Answer
The correct answer is that impersonation requires the iam.serviceAccounts.getAccessToken permission, and it can be used to delegate access across projects. This permission is essential because service account impersonation works by allowing a user or resource to call the Security Token Service (STS) to generate an access token on behalf of the target service account; without it, the STS cannot issue the token, making the entire impersonation flow impossible. On the Google Professional Cloud Security Engineer exam, this concept frequently appears in scenario-based questions about cross-project access, where a common trap is confusing the roles that grant this permission—such as the Service Account Token Creator role—with broader roles like Editor or Owner, which do not automatically include it. A reliable memory tip is to think of the getAccessToken permission as the literal key to the impersonation door: if you cannot get the token, you cannot act as the service account, regardless of other permissions you hold.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Impersonation requires the iam.serviceAccounts.getAccessToken permission.
Option C is correct because the iam.serviceAccounts.getAccessToken permission is required to generate an access token for a service account, which is the core mechanism of impersonation. Without this permission, the Security Token Service cannot issue a token on behalf of the service account, making impersonation impossible.
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.
- ✗
A user must have the roles/iam.serviceAccountUser role on the service account to impersonate it.
Why it's wrong here
Incorrect. The roles/iam.serviceAccountUser role allows a user to list service accounts and get their metadata, but not to impersonate them. Impersonation requires the roles/iam.serviceAccountTokenCreator role or the specific iam.serviceAccounts.getAccessToken permission.
- ✗
The Security Token Service (sts.googleapis.com) must be enabled for impersonation.
Why it's wrong here
Incorrect. While the Security Token Service (STS) is used to exchange tokens, enabling sts.googleapis.com is not required for service account impersonation. Impersonation uses the IAM API and the service account's credentials directly.
- ✓
Impersonation requires the iam.serviceAccounts.getAccessToken permission.
Why this is correct
Correct. The iam.serviceAccounts.getAccessToken permission is required to generate an access token for a service account, which is the core mechanism of impersonation.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Service accounts cannot impersonate other service accounts.
Why it's wrong here
Incorrect. Service accounts can impersonate other service accounts if they have the appropriate permissions. This is commonly used for cross-project access.
- ✓
Impersonation can be used to delegate access across projects.
Why this is correct
Correct. Impersonation allows a user or service account to act as another service account, enabling delegated access across projects.
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 the roles/iam.serviceAccountUser and roles/iam.serviceAccountTokenCreator roles, leading candidates to mistakenly choose Option A when impersonation actually requires the token creator role or the specific getAccessToken permission.
Detailed technical explanation
How to think about this question
Under the hood, service account impersonation works by calling the generateAccessToken method of the IAM Credentials API (iamcredentials.googleapis.com), which returns a short-lived OAuth 2.0 access token. The impersonating identity must have the iam.serviceAccounts.getAccessToken permission on the target service account, which is included in the roles/iam.serviceAccountTokenCreator role. This mechanism is commonly used in multi-project architectures where a service account in one project needs to access resources in another project without sharing keys.
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.
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FAQ
Questions learners often ask
What does this PCSE question test?
Read the scenario before looking for a memorised answer.
What is the correct answer to this question?
The correct answer is: Impersonation requires the iam.serviceAccounts.getAccessToken permission. — Option C is correct because the iam.serviceAccounts.getAccessToken permission is required to generate an access token for a service account, which is the core mechanism of impersonation. Without this permission, the Security Token Service cannot issue a token on behalf of the service account, making impersonation impossible.
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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Last reviewed: Jun 30, 2026
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