The answer is to grant the service account roles/storage.objectViewer on the bucket and remove all other bindings. This is correct because the principle of least privilege requires that you assign only the minimal permissions needed—in this case, read-only access to objects—while eliminating any existing bindings for other identities, thereby restricting the Cloud Storage bucket exclusively to that specific service account. On the Google Professional Cloud Architect exam, this scenario tests your understanding of resource-level IAM policies versus bucket-level ACLs, and a common trap is to mistakenly use a primitive role like roles/storage.legacyObjectReader or to leave inherited permissions from the project level intact, which would break the restriction. Remember the memory tip: “Bind and strip—one role, one identity, no extras.”
Google PCA Design and plan a cloud solution architecture Practice Question
This PCA practice question tests your understanding of design and plan a cloud solution architecture. 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 wants to restrict access to a Cloud Storage bucket so that only a specific service account can read objects. The bucket contains sensitive data. Which identity and access management (IAM) approach should the architect use?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Grant the service account roles/storage.objectViewer on the bucket and remove all other bindings.
Option D is correct because the principle of least privilege dictates that the service account should be granted only the minimal permissions required to read objects, which is roles/storage.objectViewer. By removing all other bindings, the bucket becomes accessible exclusively to that service account, ensuring that no other identities (users, groups, or other service accounts) can read the sensitive data. This approach directly enforces the requirement using IAM roles on the bucket resource.
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.
✗
Grant the service account roles/iam.serviceAccountUser on the bucket.
Why it's wrong here
roles/iam.serviceAccountUser is for using service accounts, not for accessing storage.
✗
Use a signed URL to allow access for the service account.
Why it's wrong here
Signed URLs are for temporary access, not for a service account.
✗
Grant the service account roles/storage.admin on the bucket.
Why it's wrong here
roles/storage.admin grants full control, which is excessive and includes write, delete, etc.
✓
Grant the service account roles/storage.objectViewer on the bucket and remove all other bindings.
Why this is correct
This restricts read access to only the service account.
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 misconception that granting a broad role like roles/storage.admin is acceptable for simplicity, but the trap here is that candidates overlook the principle of least privilege and the specific read-only requirement, leading them to choose an overly permissive role.
Detailed technical explanation
How to think about this question
Under the hood, Cloud Storage IAM roles are evaluated at the bucket level using the resource manager hierarchy; when all other bindings are removed, the bucket's IAM policy contains only the service account with roles/storage.objectViewer, which maps to the storage.objects.get and storage.objects.list permissions. In a real-world scenario, this is critical for compliance with data isolation requirements (e.g., HIPAA or PCI-DSS) where only a specific application identity should access sensitive data, and any other principal—even project editors—must be explicitly denied via an organization policy or bucket-level IAM condition.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this PCA question in full detail.
Design and plan a cloud solution architecture — This question tests Design and plan a cloud solution architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Grant the service account roles/storage.objectViewer on the bucket and remove all other bindings. — Option D is correct because the principle of least privilege dictates that the service account should be granted only the minimal permissions required to read objects, which is roles/storage.objectViewer. By removing all other bindings, the bucket becomes accessible exclusively to that service account, ensuring that no other identities (users, groups, or other service accounts) can read the sensitive data. This approach directly enforces the requirement using IAM roles on the bucket resource.
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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