PCDE Monitor and optimize database performance Practice Question
This PCDE practice question tests your understanding of monitor and optimize database 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.
You are managing a Cloud SQL for MySQL instance that supports a web application. Recently, users have reported that the application is responding slowly during peak hours. You examine the Query Insights dashboard and see that a specific query is running frequently and has a high execution time. The query involves JOINs on three tables, each with tens of thousands of rows. The query plan shows a full table scan on two tables. What should you do first to improve performance?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add indexes on the columns used in JOIN conditions.
Option C is correct: Adding appropriate indexes on the join columns will reduce full table scans, which is the most effective immediate action. Option A (increasing instance size) may help but does not address the root cause. Option B (enabling database flags like query cache) is less effective and query cache is deprecated in newer versions. Option D (rewriting the query) could help but is more complex and time-consuming; indexing is usually the first step.
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.
✗
Enable the query cache flag in Cloud SQL database flags.
Why it's wrong here
Query cache is deprecated in MySQL 8.0 and may not help with full table scans; it's not a recommended solution.
✗
Increase the instance size to provide more memory and CPU.
Why it's wrong here
Scaling up may improve overall throughput but does not fix the full table scans; it's a temporary workaround.
✓
Add indexes on the columns used in JOIN conditions.
Why this is correct
Indexes will allow the database to avoid full table scans, significantly reducing query execution time.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Rewrite the query to use subqueries instead of JOINs.
Why it's wrong here
Rewriting might help but is more complex; indexing is a simpler and more effective first step.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 PCDE exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Monitor and optimize database performance — This question tests Monitor and optimize database performance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Add indexes on the columns used in JOIN conditions. — Option C is correct: Adding appropriate indexes on the join columns will reduce full table scans, which is the most effective immediate action. Option A (increasing instance size) may help but does not address the root cause. Option B (enabling database flags like query cache) is less effective and query cache is deprecated in newer versions. Option D (rewriting the query) could help but is more complex and time-consuming; indexing is usually the first step.
What should I do if I get this PCDE question wrong?
Identify which PCDE exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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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