DBS-C01 Monitoring and Troubleshooting Practice Question
A developer is troubleshooting slow queries in Amazon RDS for MySQL. The 'Threads_running' status variable is consistently above 200. The application uses connection pooling. Which metric should be monitored to identify the root cause?
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
✓
Innodb_row_lock_current_waits
High 'Threads_running' consistently above 200 often indicates queries waiting on locks or I/O. 'Innodb_row_lock_current_waits' directly measures the number of row lock waits, which is a common cause of blocked queries when connection pooling is used. Option B is wrong because 'Queries_per_second' measures throughput, not concurrent active queries. Option C is wrong because 'Slow_queries' counts only queries exceeding a time threshold, not all concurrent queries. Option D is wrong because 'Threads_connected' shows the number of open connections, not necessarily active queries; with connection pooling, many connections may be idle.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Innodb_row_lock_current_waits
Why this is correct
High thread count with many lock waits indicates contention.
- ✗
Queries_per_second
Why it's wrong here
Throughput doesn't indicate concurrency issues.
- ✗
Slow_queries
Why it's wrong here
Slow queries are a subset; not all high threads are slow.
- ✗
Threads_connected
Why it's wrong here
Connected threads may be idle; running threads are active.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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