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 microservices application on GKE. The checkout service has high tail latency. Using Cloud Profiler, the team finds that most time is spent in database queries. Which action should they take to improve performance?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add database connection pooling using a sidecar proxy.
Option C is correct because database connection pooling reduces the overhead of establishing new connections for each request, which is a common cause of high tail latency in microservices. By using a sidecar proxy (e.g., Envoy or a dedicated connection pooler like PgBouncer), the checkout service can reuse existing database connections, minimizing latency spikes from connection setup and teardown. This directly addresses the root cause identified by Cloud Profiler—time spent in database queries—without requiring a database migration or scaling the service itself.
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.
✗
Migrate the database to Cloud Spanner.
Why it's wrong here
Spanner is a horizontal scaling solution but migration is not the best first step for connection pooling issues.
✗
Increase the number of replicas of the checkout service.
Why it's wrong here
Increasing replicas distributes traffic but does not fix slow database queries.
✓
Add database connection pooling using a sidecar proxy.
Why this is correct
Connection pooling reduces overhead of establishing connections, improving latency.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable Cloud CDN for the checkout API.
Why it's wrong here
Cloud CDN is for static content, not dynamic API calls.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that scaling out (increasing replicas) or migrating to a different database solves all performance issues, when the real problem is connection management overhead within the existing database layer.
Detailed technical explanation
How to think about this question
Database connection pooling works by maintaining a persistent set of connections to the database, which are borrowed and returned by application threads. In GKE, a sidecar proxy like Envoy can implement connection pooling at the L4/L7 layer, using HTTP/2 multiplexing to reduce the number of TCP connections and avoid the three-way handshake overhead for each request. This is especially effective in microservices with high request rates, where connection storms can cause database server CPU spikes and increased tail latency.
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: Add database connection pooling using a sidecar proxy. — Option C is correct because database connection pooling reduces the overhead of establishing new connections for each request, which is a common cause of high tail latency in microservices. By using a sidecar proxy (e.g., Envoy or a dedicated connection pooler like PgBouncer), the checkout service can reuse existing database connections, minimizing latency spikes from connection setup and teardown. This directly addresses the root cause identified by Cloud Profiler—time spent in database queries—without requiring a database migration or scaling the service itself.
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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