Quick Answer
The answer is to monitor the Binary log disk usage metric in Cloud Monitoring. Binary logs in MySQL record every data-changing statement like INSERT, UPDATE, and DELETE, and under heavy write workloads or misconfigured retention policies, these logs can rapidly consume disk space, often becoming the hidden culprit behind high disk usage in Cloud SQL for MySQL. On the Google Professional Cloud Database Engineer exam, this scenario tests your ability to distinguish between storage consumed by actual database data versus operational overhead like binary logs, transaction logs, or slow query logs—a common trap is to first check general disk usage without isolating the log component. A reliable memory tip is to think of binary logs as a running audit trail: if your writes are high, your logs will bloat, so always check the binary log disk usage metric first when troubleshooting high disk usage.
This PCDE practice question tests your understanding of monitor and optimize database performance. 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.
Your Cloud SQL for MySQL instance is experiencing unusually high disk usage. You need to identify the cause. Which metric should you monitor in Cloud Monitoring?
InnoDB row reads
Why wrong: This measures read operations, not disk usage.
CPU utilization
Why wrong: CPU is unrelated to disk space.
Query latency
Why wrong: Latency is an effect, not the cause.
Binary log disk usage
Binary logs can consume significant disk space.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Binary log disk usage
Binary logs in MySQL store all data changes (e.g., INSERT, UPDATE, DELETE) and can consume significant disk space, especially under heavy write workloads or if retention is misconfigured. Monitoring 'Binary log disk usage' directly reveals whether accumulated binary logs are the primary cause of high disk usage, which is a common issue in Cloud SQL for MySQL.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
InnoDB row reads
Why it's wrong here
This measures read operations, not disk usage.
CPU utilization
Why it's wrong here
CPU is unrelated to disk space.
Query latency
Why it's wrong here
Latency is an effect, not the cause.
Binary log disk usage
Why this is correct
Binary logs can consume significant disk space.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates may confuse performance metrics (like CPU or latency) with storage metrics, overlooking the direct disk space impact of binary logs in MySQL replication or backup configurations.
Detailed technical explanation
Binary logs are essential for point-in-time recovery and replication in MySQL; they are written sequentially and can grow unbounded if not purged via `expire_logs_days` or automated retention policies. In Cloud SQL, the default binary log retention is 7 days, but manual intervention or misconfiguration can lead to excessive accumulation, consuming disk space and potentially causing instance outages. Monitoring this metric helps differentiate between binary log bloat and other causes like data growth or temporary files.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Monitor and optimize database performance — This question tests Monitor and optimize database performance — Read the scenario before looking for a memorised answer..
The correct answer is: Binary log disk usage — Binary logs in MySQL store all data changes (e.g., INSERT, UPDATE, DELETE) and can consume significant disk space, especially under heavy write workloads or if retention is misconfigured. Monitoring 'Binary log disk usage' directly reveals whether accumulated binary logs are the primary cause of high disk usage, which is a common issue in Cloud SQL for MySQL.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
This PCDE practice question is part of Courseiva's free Google Cloud 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 PCDE exam.
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