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 runs a web application on Compute Engine behind a regional HTTP Load Balancer. Users report slow page load times during peak hours. CPU utilization on instances is under 60%, but network egress is near the instance's bandwidth limit. Which action should the engineer take?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a larger machine type with higher network throughput.
The bottleneck is network egress bandwidth, not CPU. Increasing the instance size to a machine type with higher network throughput (e.g., n2-highmem-4 vs. n2-standard-2) directly raises the per-instance egress cap, alleviating the bandwidth limit. Option D is correct because it addresses the root cause—insufficient network I/O capacity per instance.
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 instances in the instance group.
Why it's wrong here
More instances share the load but each still has the same bandwidth cap.
✗
Switch to a global external HTTP Load Balancer.
Why it's wrong here
A global LB does not increase per-instance network throughput.
✗
Enable Cloud CDN.
Why it's wrong here
CDN caches static content, but the reported slowness may be dynamic.
✓
Use a larger machine type with higher network throughput.
Why this is correct
Larger machine types have higher network egress limits, addressing the bottleneck.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that horizontal scaling (adding instances) always solves performance issues, but here the bottleneck is per-instance network throughput, not request handling capacity.
Detailed technical explanation
How to think about this question
Compute Engine machine types have a defined egress bandwidth cap (e.g., 2 Gbps for n2-standard-2, up to 32 Gbps for larger types). When egress saturates, TCP congestion control (e.g., CUBIC) reduces throughput, causing higher latency. In a real-world scenario, a web app serving large responses (e.g., video streaming or file downloads) can hit this cap even at low CPU, making machine type selection critical for network-bound workloads.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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: Use a larger machine type with higher network throughput. — The bottleneck is network egress bandwidth, not CPU. Increasing the instance size to a machine type with higher network throughput (e.g., n2-highmem-4 vs. n2-standard-2) directly raises the per-instance egress cap, alleviating the bandwidth limit. Option D is correct because it addresses the root cause—insufficient network I/O capacity per instance.
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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