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 financial services company runs a real-time trading application on GKE with 10 microservices. The application uses Cloud Spanner as the database. Recently, the team noticed increased latency during peak trading hours. Cloud Monitoring shows high CPU utilization on the Spanner nodes (averaging 80%) and increased locking contention. The team has already added secondary indexes and tuned queries. The application's latency budget is 50ms for writes and 20ms for reads. The team must reduce latency while maintaining strong consistency and meeting the budget. What should they do?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Increase the number of Spanner nodes to reduce contention and CPU load
Increasing the number of Spanner nodes directly addresses the root cause: high CPU utilization (80%) and locking contention. More nodes distribute the read/write load, reducing per-node CPU and contention, which lowers latency. This maintains strong consistency and meets the 50ms write / 20ms read budget without architectural changes.
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.
✓
Increase the number of Spanner nodes to reduce contention and CPU load
Why this is correct
More nodes improve throughput and reduce locking contention, meeting latency budgets without sacrificing consistency.
Related concept
Read the scenario before looking for a memorised answer.
✗
Change the application to use eventual consistency for read operations
Why it's wrong here
Financial applications require strong consistency; eventual consistency could cause incorrect trades.
✗
Migrate the database to Cloud Bigtable for higher throughput
Why it's wrong here
Bigtable lacks full ACID transactions and complex queries; migration risk is high and may not support the application's requirements.
✗
Implement a write buffer using Cloud Pub/Sub and batch writes to Spanner
Why it's wrong here
Batching writes adds latency that may exceed the 50ms write budget; also adds complexity.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that adding nodes only helps with storage or throughput, not latency; in Spanner, more nodes reduce CPU contention and lock waits, directly improving latency under high load.
Detailed technical explanation
How to think about this question
Cloud Spanner uses a distributed Paxos-based replication and a two-phase commit protocol for strong consistency. Increasing nodes adds more splits and processing capacity, reducing lock contention by spreading transactions across more servers. Under the hood, Spanner's TrueTime API ensures globally consistent timestamps, and adding nodes directly improves throughput and reduces queuing delays at high CPU utilization.
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: Increase the number of Spanner nodes to reduce contention and CPU load — Increasing the number of Spanner nodes directly addresses the root cause: high CPU utilization (80%) and locking contention. More nodes distribute the read/write load, reducing per-node CPU and contention, which lowers latency. This maintains strong consistency and meets the 50ms write / 20ms read budget without architectural changes.
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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