The answer is that the service account lacks the `storage.objectViewer` IAM role. This is the most likely issue because Vertex AI pipelines require this role to perform `storage.objects.get` and `storage.objects.list` operations, which are essential for reading data from a Cloud Storage path. Without these permissions, the pipeline cannot authenticate the read request, causing it to fail even if the bucket name and file path are correct. On the Google Professional Machine Learning Engineer exam, this scenario tests your understanding of how IAM roles map to specific API actions within Vertex AI workflows. A common trap is assuming that bucket-level permissions alone suffice, but the `storage.objectViewer` role is explicitly needed for object-level reads. Remember the memory tip: "To view an object, you need Object Viewer" — this ties the role name directly to the action of reading data.
PMLE Collaborating to manage data and models Practice Question
This PMLE practice question tests your understanding of collaborating to manage data and models. 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.
Refer to the exhibit. The team notices that the pipeline fails to read data from the specified Cloud Storage path. 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 service account lacks `storage.objectViewer` permission
The pipeline fails to read data from Cloud Storage because the service account lacks the `storage.objectViewer` IAM role, which grants the `storage.objects.get` and `storage.objects.list` permissions required to read objects. Without this role, the pipeline cannot authenticate or authorize the read operation, even if the bucket and path are correct.
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 does not exist
Why it's wrong here
If the bucket didn't exist, the error would be clearer; permission is more likely.
✗
The pipeline runner is incorrect
Why it's wrong here
DataflowRunner is valid for this pipeline.
✗
The region is mismatched
Why it's wrong here
Region mismatch affects Dataflow execution, not reading from GCS.
✓
The service account lacks `storage.objectViewer` permission
Why this is correct
The Dataflow service account needs read access to Cloud Storage.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the distinction between bucket-level permissions (like `storage.objectViewer`) and project-level roles, leading candidates to overlook that the service account must have the specific IAM role on the bucket or project, not just any storage role.
Detailed technical explanation
How to think about this question
Cloud Storage IAM roles are evaluated at the bucket or project level, and the `storage.objectViewer` role is the minimum required for read-only access. Under the hood, the pipeline uses the Google Cloud Client Library, which calls the `storage.objects.get` API; if the service account lacks this permission, the API returns a 403 Forbidden error, which the pipeline surfaces as a read failure. In real-world scenarios, teams often mistakenly grant `storage.legacyBucketReader` (which only lists objects but does not allow reading object data) or forget to attach the service account to the pipeline's compute 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.
Collaborating to manage data and models — This question tests Collaborating to manage data and models — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The service account lacks `storage.objectViewer` permission — The pipeline fails to read data from Cloud Storage because the service account lacks the `storage.objectViewer` IAM role, which grants the `storage.objects.get` and `storage.objects.list` permissions required to read objects. Without this role, the pipeline cannot authenticate or authorize the read operation, even if the bucket and path are correct.
What should I do if I get this PMLE 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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Question Discussion
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