The correct approach is to add the service account from Project A as a member of the bucket's IAM policy in Project B with the Storage Object Viewer role. This works because Cloud Storage IAM policies are applied at the resource level—the bucket itself—rather than at the project level, allowing you to grant cross-project cloud storage access without making the service account a member of Project B. On the Google Professional Cloud Security Engineer exam, this scenario tests your understanding of resource-level IAM binding versus project-level membership; a common trap is assuming you need to grant the service account project-level roles like Storage Object Viewer on Project B, which would over-provision permissions and violate least privilege. Instead, remember that buckets are autonomous IAM resources, so you simply attach the policy directly to the bucket. A useful memory tip: "Bind at the bucket, not the project"—if the service account needs to read from a specific bucket, add it to that bucket’s IAM policy, not the entire project.
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 uses multiple Google Cloud projects. A service account in Project A needs to read data from a Cloud Storage bucket in Project B. What is the correct way to grant access?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add the service account as a member of the bucket's IAM policy with the Storage Object Viewer role.
Option D is correct because Cloud Storage uses IAM policies at the resource (bucket) level to grant cross-project access. By adding the service account from Project A as a member of the bucket's IAM policy in Project B with the Storage Object Viewer role, you grant the service account read-only access to objects in that bucket without requiring membership in Project B itself. This follows the principle of least privilege and avoids unnecessary project-level permissions.
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.
✗
Make the bucket publicly accessible and use signed URLs.
Why it's wrong here
Public access is a security risk and not recommended.
✗
Grant the service account the Project Viewer role on Project B.
Why it's wrong here
Project Viewer does not grant access to specific resources.
✗
Add the service account as a member of Project B with the Storage Object Viewer role.
Why it's wrong here
This grants access to all buckets in Project B, violating least privilege.
✓
Add the service account as a member of the bucket's IAM policy with the Storage Object Viewer role.
Why this is correct
This grants least-privilege access specifically to the bucket.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse project-level IAM roles with resource-level IAM roles, assuming that adding a service account as a member of the target project is necessary, when in fact Cloud Storage supports direct resource-level IAM binding for cross-project access.
Detailed technical explanation
How to think about this question
Under the hood, Cloud Storage IAM policies are evaluated at the bucket level using the `storage.buckets.getIamPolicy` and `storage.buckets.setIamPolicy` methods. When a service account from Project A makes a request to read an object, the Cloud Storage backend checks the bucket's IAM policy for the service account's email, not its project membership. This allows fine-grained access control across projects without requiring the service account to be a member of the target project. A real-world scenario is a data analytics pipeline where a service account in a processing project needs to read raw data from a storage project; using bucket-level IAM avoids granting project-level access that could expose other resources.
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.
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: Add the service account as a member of the bucket's IAM policy with the Storage Object Viewer role. — Option D is correct because Cloud Storage uses IAM policies at the resource (bucket) level to grant cross-project access. By adding the service account from Project A as a member of the bucket's IAM policy in Project B with the Storage Object Viewer role, you grant the service account read-only access to objects in that bucket without requiring membership in Project B itself. This follows the principle of least privilege and avoids unnecessary project-level permissions.
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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