- A
The service account needs to be downloaded as a JSON key and added to the app configuration.
Why wrong: Using a key is unnecessary and insecure; App Engine automatically uses the service account.
- B
The bucket has uniform bucket-level access disabled, so ACLs may override IAM permissions.
Why wrong: Even with ACLs, if the service account is not granted via ACL, IAM role should still apply if set correctly.
- C
The bucket is in a VPC Service Controls perimeter that blocks access from the App Engine service account.
Why wrong: VPC-SC would result in a different error (access denied by org policy).
- D
The service account is from the app's project, not the bucket's project, and the bucket's IAM policy may not include the service account.
Cross-project IAM requires adding the service account from the source project to the bucket's IAM policy in the destination project.
Quick Answer
The answer is that the App Engine service account from the app’s own project must be explicitly granted the Storage Object Viewer role on the bucket in the bucket’s project. This is the core of cross-project IAM for Cloud Storage: IAM policies are resource-local, so a service account from Project A cannot use roles inherited from Project B’s organization or folder hierarchy. When integrating App Engine with Cloud Storage across projects, the bucket’s IAM policy must include the service account email as a member, otherwise the 403 error persists even if the account has permissions in its home project. On the Google Professional Cloud Developer exam, this scenario tests your understanding that cross-project access requires explicit resource-level grants, not just project-level roles—a common trap is assuming the service account’s project-level roles carry over. Remember the mnemonic: “Cross-project? Grant at the bucket, not the project.”
PCD Integrating Google Cloud services Practice Question
This PCD practice question tests your understanding of integrating google cloud services. 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 developer is integrating an App Engine standard environment app with Cloud Storage. The app needs to read objects from a bucket that is in a different project. The developer has granted the App Engine service account the Storage Object Viewer role on the bucket. However, the app still gets a 403 error when trying to read objects. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
The service account is from the app's project, not the bucket's project, and the bucket's IAM policy may not include the service account.
Option A is correct because cross-project access requires the service account to be granted access at the bucket level in the source project, but the App Engine service account is in the same project as the app; the bucket is in another project, so the role must be assigned in the bucket's project. The error might persist if the bucket's IAM policy doesn't include the service account. Option B is wrong as no need for service account key. Option C is wrong because VPC-SC could block, but that would be a different error. Option D is wrong because public access disabled is fine for explicit IAM.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The service account needs to be downloaded as a JSON key and added to the app configuration.
Why it's wrong here
Using a key is unnecessary and insecure; App Engine automatically uses the service account.
- ✗
The bucket has uniform bucket-level access disabled, so ACLs may override IAM permissions.
Why it's wrong here
Even with ACLs, if the service account is not granted via ACL, IAM role should still apply if set correctly.
- ✗
The bucket is in a VPC Service Controls perimeter that blocks access from the App Engine service account.
Why it's wrong here
VPC-SC would result in a different error (access denied by org policy).
- ✓
The service account is from the app's project, not the bucket's project, and the bucket's IAM policy may not include the service account.
Why this is correct
Cross-project IAM requires adding the service account from the source project to the bucket's IAM policy in the destination project.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
- Standard ACLs match source addresses.
- Extended ACLs can match source, destination, protocol and ports.
- The first matching ACL entry is used.
- There is usually an implicit deny at the end.
TExam Day Tips
- Check inbound versus outbound direction.
- Read the ACL from top to bottom.
- Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related PCD ACL questions on filtering logic and placement.
- →
Integrating Google Cloud services — study guide chapter
Learn the concepts, then practise the questions
- →
Integrating Google Cloud services practice questions
Targeted practice on this topic area only
- →
All PCD questions
500 questions across all exam domains
- →
Google Professional Cloud Developer study guide
Full concept coverage aligned to exam objectives
- →
PCD practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related PCD practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Designing highly scalable, available, and reliable cloud-native applications practice questions
Practise PCD questions linked to Designing highly scalable, available, and reliable cloud-native applications.
Building and testing applications practice questions
Practise PCD questions linked to Building and testing applications.
Deploying applications practice questions
Practise PCD questions linked to Deploying applications.
Integrating Google Cloud services practice questions
Practise PCD questions linked to Integrating Google Cloud services.
Managing application performance monitoring practice questions
Practise PCD questions linked to Managing application performance monitoring.
PCD fundamentals practice questions
Practise PCD questions linked to PCD fundamentals.
PCD scenario practice questions
Practise PCD questions linked to PCD scenario.
PCD troubleshooting practice questions
Practise PCD questions linked to PCD troubleshooting.
Practice this exam
Start a free PCD practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this PCD question test?
Integrating Google Cloud services — This question tests Integrating Google Cloud services — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: The service account is from the app's project, not the bucket's project, and the bucket's IAM policy may not include the service account. — Option A is correct because cross-project access requires the service account to be granted access at the bucket level in the source project, but the App Engine service account is in the same project as the app; the bucket is in another project, so the role must be assigned in the bucket's project. The error might persist if the bucket's IAM policy doesn't include the service account. Option B is wrong as no need for service account key. Option C is wrong because VPC-SC could block, but that would be a different error. Option D is wrong because public access disabled is fine for explicit IAM.
What should I do if I get this PCD question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related PCD ACL questions on filtering logic and placement.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Standard ACLs match source addresses.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 24, 2026
This PCD 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 PCD exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.