The correct answer is that the Dataflow worker service account needs the BigQuery Data Viewer role. This is because Dataflow workers execute under a specific service account—either the Compute Engine default or a custom one—and that account must have the BigQuery Data Viewer role to read table data from BigQuery. Without this permission, the workers cannot access source data, causing the job to fail with access errors; the BigQuery User role is insufficient for reading table data, and the BigQuery Admin role is overly permissive and unnecessary. On the Google Professional Data Engineer exam, this scenario tests your understanding of least-privilege IAM for data pipelines, often appearing as a tricky distractor where candidates confuse User and Data Viewer roles. A common trap is assuming the User role grants read access, but it only allows query execution, not direct table reads. Memory tip: think "Viewer to read, User to run"—the worker needs to view the table data before it can process it.
PDE Designing data processing systems Practice Question
This PDE practice question tests your understanding of designing data processing systems. 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.
Exhibit
Refer to the exhibit.
```json
{
"error": {
"code": 403,
"message": "The service account 'dataflow-sa@project.iam.gserviceaccount.com' does not have 'bigquery.tables.getData' permission on table 'project:dataset.table'.",
"status": "PERMISSION_DENIED"
}
}
```
This error occurs when a Dataflow pipeline tries to read from a BigQuery table.
What is the root cause of this error and the correct solution?
Refer to the exhibit.
```json
{
"error": {
"code": 403,
"message": "The service account 'dataflow-sa@project.iam.gserviceaccount.com' does not have 'bigquery.tables.getData' permission on table 'project:dataset.table'.",
"status": "PERMISSION_DENIED"
}
}
```
This error occurs when a Dataflow pipeline tries to read from a BigQuery table.
A
The BigQuery table requires authorized view access.
Why wrong: Authorized views are for granting access to underlying tables via views, not direct permission.
B
The user running the job needs the BigQuery Admin role.
Why wrong: The error involves the service account, not the user.
C
The Dataflow service account needs the BigQuery User role.
Why wrong: BigQuery User role includes limited permissions and does not include getData.
D
The Dataflow worker service account needs the BigQuery Data Viewer role.
BigQuery Data Viewer includes the required getData permission.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The Dataflow worker service account needs the BigQuery Data Viewer role.
Option D is correct because Dataflow workers execute under a specific service account (compute engine default or custom), and that service account must have the BigQuery Data Viewer role to read data from BigQuery tables. Without this permission, the workers cannot access the source data, causing the job to fail with access errors. The BigQuery User role is insufficient for reading table data, and the BigQuery Admin role is overly permissive and not required for this task.
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 BigQuery table requires authorized view access.
Why it's wrong here
Authorized views are for granting access to underlying tables via views, not direct permission.
✗
The user running the job needs the BigQuery Admin role.
Why it's wrong here
The error involves the service account, not the user.
✗
The Dataflow service account needs the BigQuery User role.
Why it's wrong here
BigQuery User role includes limited permissions and does not include getData.
✓
The Dataflow worker service account needs the BigQuery Data Viewer role.
Why this is correct
BigQuery Data Viewer includes the required getData permission.
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 the Dataflow controller service account (which manages the job) and the Dataflow worker service account (which performs data operations), leading candidates to incorrectly assign permissions to the controller account instead of the worker account.
Detailed technical explanation
How to think about this question
In Dataflow, the worker service account (often the Compute Engine default service account) is used by each worker VM to interact with Google Cloud services like BigQuery. The BigQuery Data Viewer role (roles/bigquery.dataViewer) grants the bigquery.tables.get and bigquery.tables.getData permissions, which are required to read table rows. Without these, the workers receive a 403 Access Denied error when attempting to read the source table. This is a common misconfiguration when using Dataflow with BigQuery as a source.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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.
Designing data processing systems — This question tests Designing data processing systems — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The Dataflow worker service account needs the BigQuery Data Viewer role. — Option D is correct because Dataflow workers execute under a specific service account (compute engine default or custom), and that service account must have the BigQuery Data Viewer role to read data from BigQuery tables. Without this permission, the workers cannot access the source data, causing the job to fail with access errors. The BigQuery User role is insufficient for reading table data, and the BigQuery Admin role is overly permissive and not required for this task.
What should I do if I get this PDE 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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