Google PCA Designing for Security and Compliance Practice Question
A developer wants to allow a Compute Engine VM to authenticate to Google Cloud APIs without embedding service account keys in the VM image. What is the recommended approach?
⚠ Common exam trap
Candidates often confuse service account impersonation with direct attachment; candidates may think impersonation is needed for VMs, but impersonation is for users or services acting as another identity, not for a VM's native authentication.
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
✓
Attach a service account to the VM instance
Attaching a service account to a Compute Engine VM instance is the recommended approach because it provides the VM with automatically rotated, short-lived credentials via the metadata server. Applications on the VM can call the metadata server to obtain access tokens without any key files. This eliminates the risk of key leakage and manual rotation.
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 Cloud KMS to encrypt a service account key and store it in a bucket
Why it's wrong here
Cloud KMS encrypts the key but the VM must still decrypt and load it, so a long-lived credential persists in the image or metadata. KMS protects data at rest, not workload identity; it suits encrypting buckets or disks, not removing keys from authentication.
- ✗
Use a service account impersonation flow
Why it's wrong here
Impersonation still requires a base credential on the VM to call the IAM Credentials API, so a secret remains embedded. It suits short-lived cross-project or human access, not the keyless metadata-server flow that attached service accounts provide.
- ✓
Attach a service account to the VM instance
Why this is correct
Attaching a service account to the VM lets Compute Engine supply short-lived credentials through the instance metadata server, so applications call Google Cloud APIs without embedded keys. This removes the key distribution and rotation risk that static service account keys in images create.
- ✗
Create a service account key and store it in the VM's startup script
Why it's wrong here
Storing a key in the startup script embeds a long-lived credential in the instance, exactly what the stem forbids. Startup scripts suit bootstrapping configuration; attached service accounts supply tokens via the metadata server with no key material at all.
Go deeper
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About these practice questions
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Google Cloud exam blueprint
This PCA practice question is part of Courseiva's free Google Cloud 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 PCA exam.