easyMultiple Choice
PDE Practice Question: Refer to the exhibit
Exhibit
gcloud pubsub topics get-iam-policy my-topic Bindings: - members: - serviceAccount:sa@project.iam.gserviceaccount.com role: roles/pubsub.subscriber
Refer to the exhibit. A subscriber is unable to pull messages from the topic. What is the most likely cause?
⚠ Common exam trap
Google Cloud often tests the distinction between topics and subscriptions, trapping candidates who assume that having a topic and a subscriber role is sufficient to receive messages, when in fact a subscription must be explicitly created.
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
✓
No subscription has been created for the topic.
In Google Cloud Pub/Sub, a topic is a named resource to which messages are sent by publishers. Subscribers must create a subscription (pull or push) to receive messages from that topic. If no subscription exists, the subscriber cannot pull any messages because there is no delivery endpoint or pull queue attached to the topic. Option C correctly identifies this missing subscription as the root cause.
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
Holding the subscriber role already authorises pulling, so an unspecified topic misconfiguration is not the demonstrable cause shown in the exhibit. It is tempting because subscription or topic settings can block delivery, but the exhibit points to a missing subscriber binding rather than configuration.
- ✗
The service account needs roles/pubsub.viewer to list subscriptions.
Why it's wrong here
Listing subscriptions is a control-plane operation; pulling messages requires roles/pubsub.subscriber on the subscription itself, so viewer cannot authorise the pull. It is tempting because viewer grants read access to subscription metadata, which would suffice for inspecting configuration rather than consuming messages.
- ✓
No subscription has been created for the topic.
Why this is correct
Pub/Sub delivers messages only through subscriptions; a topic without any subscription retains messages but has no consumer to pull them. The subscriber's pull fails because no subscription exists to bind the topic to a receiving endpoint.
- ✗
The service account lacks roles/pubsub.publisher.
Why it's wrong here
Publishing permission governs writing messages to a topic, not reading them from a subscription, so its absence cannot block a pull. It is tempting because the symptom concerns a topic, yet the failing operation is consumption, which requires roles/pubsub.subscriber on the subscription.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.