- A
Change the persistent disk type from pd-standard to pd-ssd.
SSD provides lower latency and higher IOPS for random write workloads, solving the problem cost-effectively.
- B
Use a regional persistent disk for higher availability and performance.
Why wrong: Regional persistent disks provide synchronous replication across zones, increasing availability but not improving latency; in fact, they may add overhead.
- C
Add more replicas of the StatefulSet to distribute writes across multiple disks.
Why wrong: Adding replicas would require application-level sharding and does not directly address disk latency; also increases complexity and cost.
- D
Increase the size of the persistent disks to improve IOPS limits.
Why wrong: Increasing disk size improves IOPS limits linearly but does not reduce latency as much as switching to SSD; also less cost-effective if size is not needed.
Quick Answer
The answer is to change the persistent disk type from pd-standard to pd-ssd. This is the most cost-effective solution because pd-standard disks are HDD-based and optimized for sequential reads, not the small random writes your MySQL database performs, leading to insufficient IOPS and a consistently high disk queue depth. By switching to pd-ssd, you gain significantly higher IOPS and lower latency for random write workloads, directly addressing the throughput drop without requiring architectural changes or over-provisioning capacity. On the Google Professional Cloud Database Engineer exam, this scenario tests your understanding of how persistent disk types map to workload patterns—specifically that pd-standard is a trap for write-heavy or random I/O workloads, while pd-ssd is the go-to for low-latency database performance. A common mistake is to over-provision disk size for more IOPS, but changing the type is cheaper and more effective. Memory tip: “SSD for random, Standard for sequential.”
PCDE Monitor and optimize database performance Practice Question
This PCDE practice question tests your understanding of monitor and optimize database 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.
Your company runs a critical application on Google Kubernetes Engine (GKE) with a StatefulSet using persistent volumes backed by Compute Engine persistent disks. The application performs frequent small random writes to a MySQL database stored on the persistent disks. You notice that the disk write latency has increased significantly, and the application's throughput has dropped. Monitoring shows that the disk queue depth is consistently high. The current disk type is pd-standard. What is the most cost-effective way to reduce write latency and improve throughput?
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
Change the persistent disk type from pd-standard to pd-ssd.
The application is experiencing high write latency due to insufficient IOPS from pd-standard disks, which are HDD-based and optimized for sequential reads, not small random writes. Changing to pd-ssd (SSD-based) provides significantly higher IOPS and lower latency for random write workloads, directly addressing the high queue depth and throughput drop. This is the most cost-effective solution because pd-ssd offers the necessary performance improvement without requiring architectural changes or over-provisioning capacity.
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.
- ✓
Change the persistent disk type from pd-standard to pd-ssd.
Why this is correct
SSD provides lower latency and higher IOPS for random write workloads, solving the problem cost-effectively.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use a regional persistent disk for higher availability and performance.
Why it's wrong here
Regional persistent disks provide synchronous replication across zones, increasing availability but not improving latency; in fact, they may add overhead.
- ✗
Add more replicas of the StatefulSet to distribute writes across multiple disks.
Why it's wrong here
Adding replicas would require application-level sharding and does not directly address disk latency; also increases complexity and cost.
- ✗
Increase the size of the persistent disks to improve IOPS limits.
Why it's wrong here
Increasing disk size improves IOPS limits linearly but does not reduce latency as much as switching to SSD; also less cost-effective if size is not needed.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may think increasing disk size (Option D) is the cheapest way to improve IOPS, but they overlook that pd-standard's IOPS/GB ratio is so low that the cost to reach equivalent pd-ssd performance would be much higher, making a disk type change the more cost-effective choice.
Detailed technical explanation
How to think about this question
Compute Engine persistent disks have IOPS limits that scale with disk size: pd-standard provides 0.75 IOPS per GB (up to 3,000 IOPS max per instance), while pd-ssd provides 30 IOPS per GB (up to 15,000 IOPS per instance). For small random writes, pd-ssd's lower latency (1-3 ms vs 5-10 ms for pd-standard) and higher IOPS directly reduce queue depth. In GKE, StatefulSets with persistent volumes use PVCs that can be resized or have their storage class changed, but changing the disk type requires recreating the volume or using a snapshot migration.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this PCDE question test?
Monitor and optimize database performance — This question tests Monitor and optimize database performance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Change the persistent disk type from pd-standard to pd-ssd. — The application is experiencing high write latency due to insufficient IOPS from pd-standard disks, which are HDD-based and optimized for sequential reads, not small random writes. Changing to pd-ssd (SSD-based) provides significantly higher IOPS and lower latency for random write workloads, directly addressing the high queue depth and throughput drop. This is the most cost-effective solution because pd-ssd offers the necessary performance improvement without requiring architectural changes or over-provisioning capacity.
What should I do if I get this PCDE 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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Last reviewed: Jun 11, 2026
This PCDE 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 PCDE exam.
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