Quick Answer
The answer is roles/storage.objectViewer and roles/pubsub.publisher. These two IAM roles together provide the exact permissions needed for a service account to read objects from Cloud Storage and publish messages to Pub/Sub, without granting any unnecessary write or administrative capabilities. roles/storage.objectViewer includes permissions like storage.objects.get and storage.objects.list, allowing read-only access to bucket objects, while roles/pubsub.publisher enables only the pubsub.topics.publish action, strictly limiting the service account to sending messages. On the Google Professional Cloud Security Engineer exam, this scenario tests your understanding of granular IAM role composition versus using broader roles like roles/storage.admin or roles/pubsub.editor, which would violate least privilege. A common trap is selecting roles/storage.legacyObjectReader, which is deprecated and includes broader legacy bucket permissions. For a quick memory tip, think “View to read, Publish to send” — the service account only needs to see objects and push messages, nothing more.
This PCSE practice question tests your understanding of configuring access within a cloud solution environment. 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 wants to implement least privilege for a service account that needs to read objects from a Cloud Storage bucket and publish messages to a Pub/Sub topic. Which TWO IAM roles should be granted to the service account? (Choose TWO)
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.
roles/storage.objectViewer
Provides read-only access to objects.
roles/pubsub.subscriber
Why wrong: Allows subscribing, not publishing.
roles/storage.admin
Why wrong: Too broad; includes delete, update, etc.
roles/pubsub.viewer
Why wrong: Read-only access to topics, cannot publish.
roles/pubsub.publisher
Allows publishing messages to topics.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
roles/storage.objectViewer
Option A is correct because roles/storage.objectViewer grants read-only access to objects in Cloud Storage buckets, which is the minimum permission needed for the service account to read objects. This role includes permissions like storage.objects.get and storage.objects.list, allowing the service account to retrieve object data without any write or administrative capabilities.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
roles/storage.objectViewer
Why this is correct
Provides read-only access to objects.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
roles/pubsub.subscriber
Why it's wrong here
Allows subscribing, not publishing.
roles/storage.admin
Why it's wrong here
Too broad; includes delete, update, etc.
roles/pubsub.viewer
Why it's wrong here
Read-only access to topics, cannot publish.
roles/pubsub.publisher
Why this is correct
Allows publishing messages to topics.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Google Cloud often tests the distinction between publisher and subscriber roles in Pub/Sub, and candidates mistakenly choose roles/pubsub.subscriber (Option B) thinking it covers publishing, when in fact it only allows consuming messages from a subscription.
Detailed technical explanation
Under the hood, IAM roles are collections of permissions; roles/storage.objectViewer includes the storage.objects.get permission, which is used in the HTTP GET request to download an object, while roles/pubsub.publisher includes the pubsub.topics.publish permission, which is required for the Pub/Sub publish RPC. In a real-world scenario, if the service account also needed to create subscriptions or manage topics, additional roles would be required, but for the stated tasks, these two roles provide the exact set of permissions without over-provisioning.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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.
What to study next
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FAQ
Configuring access within a cloud solution environment — This question tests Configuring access within a cloud solution environment — Read the scenario before looking for a memorised answer..
The correct answer is: roles/storage.objectViewer — Option A is correct because roles/storage.objectViewer grants read-only access to objects in Cloud Storage buckets, which is the minimum permission needed for the service account to read objects. This role includes permissions like storage.objects.get and storage.objects.list, allowing the service account to retrieve object data without any write or administrative capabilities.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "least". You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
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