The answer is a PersistentVolumeClaim with RWX access mode. This is correct because RWX, or ReadWriteMany, allows multiple pods across different nodes to simultaneously read and write to the same persistent volume, which is exactly what a stateful service needs when data must be accessible from any pod in the cluster regardless of node placement. On the Google Professional Cloud Developer exam, this question tests your understanding of GKE storage access modes and how they map to shared storage solutions like Filestore or NFS. A common trap is confusing RWX with RWO (ReadWriteOnce), which only allows a single pod to mount the volume, or with ReadOnlyMany, which permits multiple readers but no writers. Remember the memory tip: "Many pods need Many writes" — RWX is for shared, concurrent read-write access across the cluster.
PCD Practice Question: Designing highly scalable, available, and reliable cloud-native applications
This PCD practice question tests your understanding of designing highly scalable, available, and reliable cloud-native applications. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 stateful service on GKE needs to persist data that must be accessible from any pod in the cluster, regardless of which node the pod runs on. Which volume type should they use?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
PersistentVolumeClaim with RWX access mode
A PersistentVolumeClaim (PVC) with RWX (ReadWriteMany) access mode is correct because it allows multiple pods across different nodes to read and write to the same persistent volume simultaneously. This is essential for a stateful service where data must be accessible from any pod in the cluster, regardless of which node the pod runs on. RWX is typically backed by network filesystems like NFS or GKE Filestore, which provide shared access across nodes.
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.
✓
PersistentVolumeClaim with RWX access mode
Why this is correct
PersistentVolumeClaim with ReadWriteMany allows multiple pods to access the same volume concurrently, even across nodes.
Related concept
Read the scenario before looking for a memorised answer.
✗
emptyDir
Why it's wrong here
emptyDir volumes are ephemeral and not shared across pods on different nodes.
✗
ConfigMap
Why it's wrong here
ConfigMaps are for configuration data and are not suitable for persistent storage.
✗
hostPath
Why it's wrong here
hostPath mounts a directory from the node's filesystem, so it is not accessible from pods on other nodes.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between access modes (RWO, RWM, RWX) and candidates mistakenly choose hostPath or emptyDir because they think local storage is sufficient, overlooking the requirement for cross-node accessibility.
Detailed technical explanation
How to think about this question
Under the hood, RWX access mode relies on a shared filesystem protocol such as NFSv4 or SMB/CIFS, which uses a lock manager to coordinate concurrent writes from multiple clients. In GKE, this is often implemented using Filestore instances, which provide a fully managed NFS server with high availability. A subtle behavior is that RWX volumes require the underlying storage backend to support distributed locking and cache coherency; otherwise, concurrent writes can lead to data corruption or stale reads, making it critical to choose a backend that guarantees consistency.
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.
Designing highly scalable, available, and reliable cloud-native applications — This question tests Designing highly scalable, available, and reliable cloud-native applications — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: PersistentVolumeClaim with RWX access mode — A PersistentVolumeClaim (PVC) with RWX (ReadWriteMany) access mode is correct because it allows multiple pods across different nodes to read and write to the same persistent volume simultaneously. This is essential for a stateful service where data must be accessible from any pod in the cluster, regardless of which node the pod runs on. RWX is typically backed by network filesystems like NFS or GKE Filestore, which provide shared access across nodes.
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.
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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