The answer is that no subscription has been created for the topic. In Google Cloud Pub/Sub, a topic is simply a named channel for publishing messages, but subscribers cannot directly pull messages from it; they must pull from a dedicated subscription resource that is attached to that topic. This subscription manages message delivery, acknowledgment, and retention, so without one, the subscriber has no endpoint to receive messages from. On the Google Professional Data Engineer exam, this concept tests your understanding of the Pub/Sub resource hierarchy, and a common trap is confusing the subscriber’s IAM role on the topic with the need for a subscription object. Remember that a topic is like a broadcast antenna, but you need a subscription as your receiver to tune in and pull the signal.
PDE Ensuring solution quality Practice Question
This PDE practice question tests your understanding of ensuring solution quality. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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. A subscriber is unable to pull messages from the topic. 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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
No subscription has been created for the topic.
Option B is correct because a subscription must exist for pulling messages; the topic alone is not enough. Option A (publisher role) is not needed for subscribers. Option C (subscriber role on topic) is correct but the subscriber also needs to have a subscription. Option D (viewer role) is irrelevant.
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 service account has the subscriber role but the topic is not configured correctly.
Why it's wrong here
The subscriber role on the topic is necessary but not sufficient without a subscription.
✗
The service account needs roles/pubsub.viewer to list subscriptions.
Why it's wrong here
The viewer role is not required for pulling; the subscriber role is sufficient.
✓
No subscription has been created for the topic.
Why this is correct
A subscription is required to pull messages; the topic only provides the ability to publish.
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.
✗
The service account lacks roles/pubsub.publisher.
Why it's wrong here
The subscriber does not need the publisher role.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 PDE exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Ensuring solution quality — This question tests Ensuring solution quality — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: No subscription has been created for the topic. — Option B is correct because a subscription must exist for pulling messages; the topic alone is not enough. Option A (publisher role) is not needed for subscribers. Option C (subscriber role on topic) is correct but the subscriber also needs to have a subscription. Option D (viewer role) is irrelevant.
What should I do if I get this PDE question wrong?
Identify which PDE exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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This PDE 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 PDE exam.
Question Discussion
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