This PCD practice question tests your understanding of integrating google cloud services. 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. A developer configured a Pub/Sub push subscription to a Cloud Run service. Messages are not being delivered to the Cloud Run service. The developer verified that the service is running and the IAM permissions are correct. 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.
The service account does not have the pubsub.publisher role
Why wrong: The pubsub.publisher role is for publishing messages, not for receiving push deliveries. The push subscription's service account needs the token creator role to generate OIDC tokens for authentication.
B
The OIDC token audience does not match the Cloud Run service's URL
Correct. The OIDC token audience must exactly match the Cloud Run service's URL. If the audience in the push subscription configuration differs from the service URL, authentication fails and messages are not delivered.
C
The push endpoint URL is not a valid HTTPS endpoint
Why wrong: Incorrect. The push endpoint is a valid HTTPS URL as shown in the exhibit. The issue is not URL validity.
D
The ackDeadlineSeconds is too short for the Cloud Run service to process messages
Why wrong: The ackDeadlineSeconds setting affects message acknowledgment timing, but messages are not being delivered at all, so this is not the likely issue.
The answer is an OIDC audience mismatch, specifically that the OIDC token audience does not match the Cloud Run service's URL. This is the most likely issue because when a Pub/Sub push subscription is configured to authenticate to a Cloud Run service using an OIDC token, the audience claim in that token must exactly match the push endpoint URL of the service. If the audience is set to a generic URL like 'https://my-service.run.app/' but the actual Cloud Run service has a unique generated hash in its URL, the authentication handshake fails and messages are never delivered, even if IAM permissions are correct. On the Google Professional Cloud Developer exam, this scenario tests your understanding of how Pub/Sub push authentication works with serverless endpoints, and the common trap is assuming that IAM roles alone guarantee delivery. Remember: the audience is not just a formality—it must be an exact string match to the service’s URL, including the trailing slash. Memory tip: “Audience equals endpoint, or your messages will end.”
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
✓
The OIDC token audience does not match the Cloud Run service's URL
The most likely issue is that the OIDC token audience does not match the Cloud Run service's URL (Option B). For push subscriptions with OIDC authentication, the audience must exactly match the service URL. Option A is incorrect because the service account needs the token creator role, not the pubsub.publisher role. Option C is incorrect because the endpoint shown is HTTPS. Option D is incorrect because ackDeadlineSeconds affects processing time, not delivery; messages not being delivered indicates an authentication or endpoint issue.
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 does not have the pubsub.publisher role
Why it's wrong here
The pubsub.publisher role is for publishing messages, not for receiving push deliveries. The push subscription's service account needs the token creator role to generate OIDC tokens for authentication.
✓
The OIDC token audience does not match the Cloud Run service's URL
Why this is correct
Correct. The OIDC token audience must exactly match the Cloud Run service's URL. If the audience in the push subscription configuration differs from the service URL, authentication fails and messages are not delivered.
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 push endpoint URL is not a valid HTTPS endpoint
Why it's wrong here
Incorrect. The push endpoint is a valid HTTPS URL as shown in the exhibit. The issue is not URL validity.
✗
The ackDeadlineSeconds is too short for the Cloud Run service to process messages
Why it's wrong here
The ackDeadlineSeconds setting affects message acknowledgment timing, but messages are not being delivered at all, so this is not the likely issue.
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.
Trap categories for this question
Command / output trap
Incorrect. The push endpoint is a valid HTTPS URL as shown in the exhibit. The issue is not URL validity.
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 PCD 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.
Integrating Google Cloud services — This question tests Integrating Google Cloud services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The OIDC token audience does not match the Cloud Run service's URL — The most likely issue is that the OIDC token audience does not match the Cloud Run service's URL (Option B). For push subscriptions with OIDC authentication, the audience must exactly match the service URL. Option A is incorrect because the service account needs the token creator role, not the pubsub.publisher role. Option C is incorrect because the endpoint shown is HTTPS. Option D is incorrect because ackDeadlineSeconds affects processing time, not delivery; messages not being delivered indicates an authentication or endpoint issue.
What should I do if I get this PCD question wrong?
Identify which PCD 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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Question Discussion
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