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 team notices that Cloud SQL read replicas are not handling read traffic efficiently, causing high latency for read-heavy queries. What is the best approach to improve read performance?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use Cloud Memorystore to cache frequent query results
Cloud Memorystore (Redis) caches the results of frequent read queries, reducing the load on Cloud SQL read replicas and lowering latency for repeated queries. This directly addresses the root cause of inefficient read traffic by serving cached data from in-memory storage, which is orders of magnitude faster than querying a replica. It is the best approach because it offloads read-heavy workloads without requiring additional replicas or relying on deprecated features like MySQL query cache.
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.
✗
Use a connection pooling proxy like ProxySQL
Why it's wrong here
Connection pooling improves connection efficiency but does not reduce query execution time or cache results.
✓
Use Cloud Memorystore to cache frequent query results
Why this is correct
Caching reduces database load and latency for read-heavy, repetitive queries.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable MySQL query cache
Why it's wrong here
Query cache is deprecated and does not scale for large workloads; it can even cause contention.
✗
Increase the number of read replicas
Why it's wrong here
More replicas help distribute load but do not optimize query performance; caching is more effective for repeated queries.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that adding more read replicas is always the best solution for read performance, but the trap here is that replicas still execute queries against disk and do not eliminate redundant work, whereas caching directly reduces query execution frequency and latency.
Detailed technical explanation
How to think about this question
Cloud Memorystore uses Redis in-memory data structures to cache query results with configurable TTL, enabling sub-millisecond response times for cached queries. Under the hood, Redis stores data as key-value pairs, and the application must implement cache-aside or write-through patterns to maintain consistency with Cloud SQL. In a real-world scenario, a social media app with trending posts can reduce Cloud SQL read replica load by 80% by caching the top 100 queries, while dynamic queries with low cache hit rates still hit the replicas.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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 Cloud Memorystore to cache frequent query results — Cloud Memorystore (Redis) caches the results of frequent read queries, reducing the load on Cloud SQL read replicas and lowering latency for repeated queries. This directly addresses the root cause of inefficient read traffic by serving cached data from in-memory storage, which is orders of magnitude faster than querying a replica. It is the best approach because it offloads read-heavy workloads without requiring additional replicas or relying on deprecated features like MySQL query cache.
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.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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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