The correct answer is that the production cluster's node pool has not been granted access to pull images from Artifact Registry in the staging project. This is because cross-project image pull permissions for a GKE node pool are not automatic; by default, each node pool uses the Compute Engine default service account, which only has access to Artifact Registry repositories within its own project. When the production cluster in a different project tries to pull the custom container image, it fails with an ImagePullErr because that service account lacks the Artifact Registry Reader role on the staging project’s repository. On the Google Professional Cloud Developer exam, this scenario tests your understanding of GKE identity and access management across projects—a common trap is assuming that images in Artifact Registry are globally accessible or that Cloud Deploy handles permissions. Remember the key: a node pool’s service account must be explicitly granted the reader role on the remote repository. A useful memory tip is “same project, no problem; cross project, grant it.”
PCD Building and testing applications Practice Question
This PCD practice question tests your understanding of building and testing applications. 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.
A company deploys a microservice on Google Kubernetes Engine (GKE) with a Cloud Deploy delivery pipeline. The application uses a custom container image stored in Artifact Registry. After a successful deployment to a staging cluster, the production deployment fails with 'ImagePullErr: image not found'. The staging and production clusters are in different projects. 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
✓
The production cluster's node pool has not been granted access to pull images from Artifact Registry in the staging project.
Option C is correct because the production cluster's node pool, which runs in a different project, does not have the necessary permissions to pull the custom container image from Artifact Registry in the staging project. By default, GKE node pools use the Compute Engine default service account, which only has access to images in the same project. To pull images across projects, the node pool's service account must be granted the Artifact Registry Reader role (roles/artifactregistry.reader) on the repository in the staging project.
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 Cloud Deploy service account lacks permission to create pods in the production cluster.
Why it's wrong here
That would cause authorization errors, not ImagePullErr.
✗
Cloud Deploy is not configured to use Artifact Registry and still references Container Registry.
Why it's wrong here
Cloud Deploy uses the registry specified in the manifest.
✓
The production cluster's node pool has not been granted access to pull images from Artifact Registry in the staging project.
Why this is correct
Cross-project image pulling requires appropriate IAM on the registry.
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 container image tag used in production is different from the staging tag.
Why it's wrong here
Same pipeline likely uses same tag.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that Cloud Deploy handles cross-project image access automatically, when in reality the node pool's service account must be explicitly granted permissions on the Artifact Registry repository in the source project.
Detailed technical explanation
How to think about this question
When a GKE node pulls a container image, it uses the node's service account to authenticate to the container registry. For cross-project access, you must grant the node's service account (or a Google service account attached to the node pool) the appropriate IAM role on the Artifact Registry repository. This is often overlooked because within the same project, the default Compute Engine service account has the Artifact Registry Reader role automatically via the 'storage.objectViewer' role on the project level, but cross-project access requires explicit IAM policy binding. The error 'ImagePullErr: image not found' can also occur if the image path is incorrect, but here the path is correct; the issue is authorization.
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.
TExam Day Tips
→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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Building and testing applications — This question tests Building and testing applications — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The production cluster's node pool has not been granted access to pull images from Artifact Registry in the staging project. — Option C is correct because the production cluster's node pool, which runs in a different project, does not have the necessary permissions to pull the custom container image from Artifact Registry in the staging project. By default, GKE node pools use the Compute Engine default service account, which only has access to images in the same project. To pull images across projects, the node pool's service account must be granted the Artifact Registry Reader role (roles/artifactregistry.reader) on the repository in the staging project.
What should I do if I get this PCD question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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