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.
Exhibit
Function CPU Time (ms) %
getCustomerData() 1200 60%
processOrder() 400 20%
saveToDatabase() 300 15%
other 100 5%
Total 2000
Refer to the exhibit. The team wants to reduce the service's p50 latency from 2 seconds to under 500ms. Which optimization would have the most impact?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Optimize getCustomerData() by caching customer data
The exhibit shows that getCustomerData() is the most time-consuming operation, taking 1.2 seconds out of the total 2-second p50 latency. Caching customer data eliminates repeated expensive lookups (e.g., database queries or external API calls), directly reducing the critical path latency. This optimization targets the largest bottleneck, making it the most impactful for achieving sub-500ms p50.
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 service instances
Why it's wrong here
More instances spread load but do not reduce per-request latency caused by CPU-bound functions.
✗
Optimize processOrder() by reducing logging
Why it's wrong here
20% improvement is helpful but not enough to reach sub-500ms.
✓
Optimize getCustomerData() by caching customer data
Why this is correct
Caching eliminates the 1200ms function call, potentially reducing total time by over 50%.
Related concept
Read the scenario before looking for a memorised answer.
✗
Optimize saveToDatabase() by using batch writes
Why it's wrong here
This function uses only 15% of CPU time, so improvement has limited impact.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that horizontal scaling or optimizing non-critical paths (like logging) can significantly reduce p50 latency, when in fact the largest single bottleneck must be addressed first.
Detailed technical explanation
How to think about this question
Caching customer data can be implemented using an in-memory cache like Redis or Memcached with a TTL, reducing p50 latency by avoiding repeated database or API calls. Under the hood, cache hits bypass I/O-bound operations, cutting latency from milliseconds to microseconds. In real-world scenarios, a cache miss still incurs the original latency, so a high hit ratio (e.g., >95%) is critical for sustained p50 improvement.
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.
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: Optimize getCustomerData() by caching customer data — The exhibit shows that getCustomerData() is the most time-consuming operation, taking 1.2 seconds out of the total 2-second p50 latency. Caching customer data eliminates repeated expensive lookups (e.g., database queries or external API calls), directly reducing the critical path latency. This optimization targets the largest bottleneck, making it the most impactful for achieving sub-500ms p50.
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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