PCDOE Optimizing service performance Practice Question
This PCDOE practice question tests your understanding of optimizing service performance. 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 company has a stateful application deployed on a GKE cluster with stateful sets using persistent volumes. The application is experiencing higher than expected latency for write operations. The team uses SSDs for persistent disks. Cloud Monitoring shows high disk queue depth on the nodes where the stateful pods are scheduled. Which of the following is the most effective optimization?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable disk caching on the persistent disks.
Option C is correct because enabling read/write caching on persistent disks reduces write latency by buffering writes to the local instance's SSD before acknowledging them to the application. This directly addresses the high disk queue depth observed in Cloud Monitoring, as caching absorbs bursty write I/O and lowers queue depth. For stateful workloads on GKE with SSDs, disk caching is a standard optimization to improve write performance without changing the underlying disk type.
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.
✗
Configure a separate node pool with local SSDs for the stateful workloads.
Why it's wrong here
Local SSDs are ephemeral and not suitable for stateful persistence.
✗
Increase the number of replicas of the stateful set.
Why it's wrong here
Adding replicas does not reduce disk queue depth on the existing nodes.
✓
Enable disk caching on the persistent disks.
Why this is correct
Disk caching can significantly reduce I/O latency if supported by the workload.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use regional persistent disks for higher throughput.
Why it's wrong here
Regional PD provides synchronous replication for HA, not higher throughput.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that local SSDs are always better for performance, but the trap here is that local SSDs lack data persistence, making them inappropriate for stateful sets that require durable storage across pod lifecycle events.
Detailed technical explanation
How to think about this question
GCE persistent disks support two caching modes: READ_WRITE (default for SSDs) and READ_ONLY. With READ_WRITE caching, writes are first committed to the local NVMe cache on the host machine and then asynchronously flushed to the persistent disk, reducing write latency by up to 80% for bursty workloads. The disk queue depth metric in Cloud Monitoring reflects the number of pending I/O requests; enabling caching allows the guest OS to absorb writes faster, lowering queue depth and improving application-perceived latency.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
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.
Optimizing service performance — This question tests Optimizing service performance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Enable disk caching on the persistent disks. — Option C is correct because enabling read/write caching on persistent disks reduces write latency by buffering writes to the local instance's SSD before acknowledging them to the application. This directly addresses the high disk queue depth observed in Cloud Monitoring, as caching absorbs bursty write I/O and lowers queue depth. For stateful workloads on GKE with SSDs, disk caching is a standard optimization to improve write performance without changing the underlying disk type.
What should I do if I get this PCDOE 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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