The answer is that the bucket’s ACLs deny Alice upload access, creating a Cloud Storage ACL vs IAM conflict. This occurs because Cloud Storage evaluates both IAM policies and Access Control Lists (ACLs) for a bucket, and an explicit ACL denial—such as lacking the `WRITER` or `OWNER` permission—overrides any broader IAM role that would otherwise allow uploads. Bob can view objects because his IAM `roles/storage.objectViewer` role is not contradicted by a restrictive ACL entry. On the Google Professional Cloud Security Engineer exam, this scenario tests your understanding of the dual authorization model; a common trap is assuming IAM alone governs access, when ACLs can silently block operations. Remember the memory tip: “IAM gives the key, but ACL locks the door”—always check both when uploads fail.
PCSE Ensuring data protection Practice Question
This PCSE practice question tests your understanding of ensuring data protection. 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 reviews the IAM policy for a Cloud Storage bucket as shown in the exhibit. Alice reports that she cannot upload objects to the bucket, while Bob can view objects. What is the most likely issue?
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The bucket has ACLs that deny Alice upload access.
Option A is correct because Cloud Storage buckets can have both IAM policies and Access Control Lists (ACLs) applied. If the bucket's ACL explicitly denies Alice the `WRITER` or `OWNER` permission, she will be unable to upload objects even if her IAM policy grants broader roles. Bob can view objects because his IAM role (e.g., `roles/storage.objectViewer`) is not overridden by a conflicting ACL, or his ACL entry grants `READER` access.
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.
✓
The bucket has ACLs that deny Alice upload access.
Why this is correct
If uniform bucket-level access is not enabled, ACLs can override IAM.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Alice has the objectViewer role but not the objectAdmin role.
Why it's wrong here
Alice has both roles, including objectAdmin.
✗
Alice does not have the storage.buckets.getIamPolicy permission.
Why it's wrong here
That permission is not needed for uploading objects.
✗
The objectAdmin role does not include the storage.objects.create permission.
Why it's wrong here
objectAdmin includes storage.objects.create.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that IAM policies alone control all access to Cloud Storage, ignoring that ACLs can override or deny permissions, leading candidates to incorrectly blame missing roles or permissions rather than a conflicting ACL.
Detailed technical explanation
How to think about this question
Cloud Storage supports two access control systems: IAM (for bucket-level permissions) and ACLs (for object-level or bucket-level fine-grained control). ACLs can grant or deny specific permissions to users, and a DENY ACL entry takes precedence over IAM grants. This dual system can lead to unexpected denials when ACLs are misconfigured, especially in hybrid environments where legacy ACLs coexist with IAM. The `storage.objects.create` permission is required to upload objects, and it is included in both `roles/storage.objectAdmin` and `roles/storage.legacyBucketWriter`.
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.
Ensuring data protection — This question tests Ensuring data protection — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The bucket has ACLs that deny Alice upload access. — Option A is correct because Cloud Storage buckets can have both IAM policies and Access Control Lists (ACLs) applied. If the bucket's ACL explicitly denies Alice the `WRITER` or `OWNER` permission, she will be unable to upload objects even if her IAM policy grants broader roles. Bob can view objects because his IAM role (e.g., `roles/storage.objectViewer`) is not overridden by a conflicting ACL, or his ACL entry grants `READER` access.
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.
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?
Read the scenario before looking for a memorised answer.
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