- A
Increase the maximum number of connections (max_connections) to 500.
Why wrong: Increasing max_connections allows more simultaneous connections, which could increase CPU load, not decrease it.
- B
Enable the MySQL slow query log and analyze the queries.
Why wrong: This is a diagnostic step, not a solution. It can help identify problematic queries, but the question asks for a resolution.
- C
Increase the MySQL query cache size (query_cache_size) to 256 MB.
The query cache stores results of SELECT queries, so repeated queries can be served from cache, reducing CPU usage and avoiding execution of the same queries.
- D
Increase the InnoDB buffer pool size to 20 GB.
Why wrong: While increasing buffer pool can reduce disk reads, the issue is CPU-bound due to repeated execution of the same queries. The buffer pool mainly affects I/O, not CPU.
Quick Answer
The correct choice is to increase the MySQL query cache size to 256 MB, as this directly addresses the performance bottleneck in a read-heavy workload by caching the result sets of repeated SELECT queries, thereby reducing the CPU and disk I/O overhead that causes the intermittent spikes. When the query cache is too small or disabled, MySQL must re-execute identical queries from scratch, which explains the high CPU usage from the mysqld process and the long execution times in the slow query log. On the LFCS exam, this scenario tests your ability to diagnose MySQL performance issues under load and apply targeted tuning—a common trap is to focus on Apache or kernel parameters instead of the database layer. Remember that for read-heavy databases, the query cache is your first lever; a quick memory tip is “cache the reads, save the seeds” to recall that caching repeated queries reduces the need to re-scan tables.
LFCS Operation of Running Systems Practice Question
This LFCS practice question tests your understanding of operation of running systems. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 a systems administrator for a company that runs a high-traffic web application on a Linux server with 32 GB of RAM and 8 CPU cores. The application uses Apache with mod_php and MySQL. Recently, the server has been experiencing intermittent slowdowns, especially during peak hours. Monitoring tools show that the CPU usage spikes to 100% for several minutes and then returns to normal. The 'top' command shows that the 'mysqld' process is often the top CPU consumer during these spikes. You notice that the MySQL slow query log contains many entries with long execution times. The database is heavily used by the web application for read-heavy workloads. After analyzing the situation, you suspect that the issue is related to MySQL configuration. Which of the following actions is most likely to resolve the performance issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Increase the MySQL query cache size (query_cache_size) to 256 MB.
Option C is correct because increasing the query cache size can significantly improve performance for read-heavy workloads with repeated identical queries, as it caches the result set of SELECT queries. The symptoms—CPU spikes from mysqld, many slow queries, and a read-heavy workload—indicate that the query cache is likely too small or disabled, causing MySQL to repeatedly execute expensive queries instead of serving cached results. A larger query cache reduces disk I/O and CPU usage for repeated queries, directly addressing the intermittent slowdowns.
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 maximum number of connections (max_connections) to 500.
Why it's wrong here
Increasing max_connections allows more simultaneous connections, which could increase CPU load, not decrease it.
- ✗
Enable the MySQL slow query log and analyze the queries.
Why it's wrong here
This is a diagnostic step, not a solution. It can help identify problematic queries, but the question asks for a resolution.
- ✓
Increase the MySQL query cache size (query_cache_size) to 256 MB.
Why this is correct
The query cache stores results of SELECT queries, so repeated queries can be served from cache, reducing CPU usage and avoiding execution of the same queries.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Increase the InnoDB buffer pool size to 20 GB.
Why it's wrong here
While increasing buffer pool can reduce disk reads, the issue is CPU-bound due to repeated execution of the same queries. The buffer pool mainly affects I/O, not CPU.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume increasing the InnoDB buffer pool size (option D) is always the best fix for MySQL performance, but the question's specific context of read-heavy workloads with repeated queries and CPU spikes makes query cache tuning more directly impactful, while a too-large buffer pool can cause memory pressure.
Detailed technical explanation
How to think about this question
The MySQL query cache stores the exact text of a SELECT query along with its result set; on subsequent identical queries, MySQL returns the cached result without executing the query again, reducing CPU and disk I/O. However, the query cache is invalidated on any write to the involved tables, so it is most effective for read-heavy workloads with infrequent writes. In MySQL 8.0, the query cache was removed due to scalability issues on multi-core systems, but in older versions (like those typical for LFCS), it remains a critical tuning parameter for such scenarios.
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 practitioner preparing for the LFCS exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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.
- →
Operation of Running Systems — study guide chapter
Learn the concepts, then practise the questions
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FAQ
Questions learners often ask
What does this LFCS question test?
Operation of Running Systems — This question tests Operation of Running Systems — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Increase the MySQL query cache size (query_cache_size) to 256 MB. — Option C is correct because increasing the query cache size can significantly improve performance for read-heavy workloads with repeated identical queries, as it caches the result set of SELECT queries. The symptoms—CPU spikes from mysqld, many slow queries, and a read-heavy workload—indicate that the query cache is likely too small or disabled, causing MySQL to repeatedly execute expensive queries instead of serving cached results. A larger query cache reduces disk I/O and CPU usage for repeated queries, directly addressing the intermittent slowdowns.
What should I do if I get this LFCS 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: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 11, 2026
This LFCS practice question is part of Courseiva's free Linux Foundation certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the LFCS exam.
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