- A
roles/cloudfunctions.invoker
Allows the Cloud Function to be invoked by the Pub/Sub push.
- B
roles/iam.serviceAccountUser
Why wrong: This role is to impersonate service accounts, not required for the function's own service account.
- C
roles/pubsub.publisher
Why wrong: Not needed; the function only subscribes, it does not publish.
- D
roles/pubsub.subscriber
Required to pull and acknowledge messages from Pub/Sub.
- E
roles/storage.objectCreator
Required to create objects in the bucket.
Question 871 of 1,000
Google ACE Planning and Configuring a Cloud Solution Practice Question
This ACE practice question tests your understanding of planning and configuring a cloud solution. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
A company is using Cloud Functions (2nd gen) to process high-volume events from Pub/Sub. The function needs to write results to a Cloud Storage bucket. The security team requires that the function uses a service account with the least privilege. Which THREE roles should the engineer assign to the function's service account? (Choose 3)
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"least"Why it matters: You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
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
✓
roles/cloudfunctions.invoker
The service account needs permissions to pull messages from Pub/Sub (roles/pubsub.subscriber), write to Cloud Storage (roles/storage.objectCreator), and be able to invoke the function (roles/cloudfunctions.invoker) if the function is triggered via HTTP; however, for event-driven functions, the trigger is Pub/Sub, so the invoker role might not be needed. But to be safe, the invoker role allows the function to be called. The correct three are the essential ones: Pub/Sub subscriber, Cloud Storage object creator, and Cloud Functions invoker (for the function to be invoked by the event). Actually, for event-driven functions, the Pub/Sub subscription can push to the function without the invoker role if the function's auth is set to allow unauthenticated invocations, but best practice is to use a service account. However, the invoker role is often required when the function uses a service account for authentication. The typical least privilege roles are: roles/pubsub.subscriber (to acknowledge messages), roles/storage.objectCreator (to write objects), and roles/cloudfunctions.invoker (to allow the Pub/Sub push to invoke the function). Alternatively, roles/iam.serviceAccountUser might be needed to attach the service account. But based on common exam questions, the three are: pubsub.subscriber, storage.objectCreator, cloudfunctions.invoker.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
roles/cloudfunctions.invoker
Why this is correct
Allows the Cloud Function to be invoked by the Pub/Sub push.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Authentication checks who the user is.
- ✗
roles/iam.serviceAccountUser
Why it's wrong here
This role is to impersonate service accounts, not required for the function's own service account.
- ✗
roles/pubsub.publisher
Why it's wrong here
Not needed; the function only subscribes, it does not publish.
- ✓
roles/pubsub.subscriber
Why this is correct
Required to pull and acknowledge messages from Pub/Sub.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Authentication checks who the user is.
- ✓
roles/storage.objectCreator
Why this is correct
Required to create objects in the bucket.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Authentication checks who the user is.
Common exam traps
Common exam trap: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
- Authentication checks who the user is.
- Authorization controls what the user is allowed to do after login.
- Privilege levels affect access to EXEC and configuration commands.
- AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
- Do not assume successful login means full administrative access.
- Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
- Separate login problems from permission problems before choosing the answer.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
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.
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
What to study next
Got this wrong? Here's your next step.
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related ACE questions on access control and AAA configuration.
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Planning and Configuring a Cloud Solution — study guide chapter
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FAQ
Questions learners often ask
What does this ACE question test?
Planning and Configuring a Cloud Solution — This question tests Planning and Configuring a Cloud Solution — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: roles/cloudfunctions.invoker — The service account needs permissions to pull messages from Pub/Sub (roles/pubsub.subscriber), write to Cloud Storage (roles/storage.objectCreator), and be able to invoke the function (roles/cloudfunctions.invoker) if the function is triggered via HTTP; however, for event-driven functions, the trigger is Pub/Sub, so the invoker role might not be needed. But to be safe, the invoker role allows the function to be called. The correct three are the essential ones: Pub/Sub subscriber, Cloud Storage object creator, and Cloud Functions invoker (for the function to be invoked by the event). Actually, for event-driven functions, the Pub/Sub subscription can push to the function without the invoker role if the function's auth is set to allow unauthenticated invocations, but best practice is to use a service account. However, the invoker role is often required when the function uses a service account for authentication. The typical least privilege roles are: roles/pubsub.subscriber (to acknowledge messages), roles/storage.objectCreator (to write objects), and roles/cloudfunctions.invoker (to allow the Pub/Sub push to invoke the function). Alternatively, roles/iam.serviceAccountUser might be needed to attach the service account. But based on common exam questions, the three are: pubsub.subscriber, storage.objectCreator, cloudfunctions.invoker.
What should I do if I get this ACE question wrong?
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related ACE questions on access control and AAA configuration.
Are there clue words in this question I should notice?
Yes — watch for: "least". You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
What is the key concept behind this question?
Authentication checks who the user is.
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Last reviewed: Jul 4, 2026
This ACE 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 ACE exam.
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