MariaDB High CPU Usage: Causes, Checks and Fixes

MariaDBhigh CPUslow queriesindexesperformance

What this problem usually means

MariaDB high CPU usually means the database is doing expensive work: table scans, joins without indexes, too many concurrent queries, maintenance jobs, or application code repeatedly asking inefficient questions.

Production caution: Killing queries can reduce load temporarily, but the real fix is usually indexing, query changes, workload control or scheduling.

Common symptoms

mysqld uses high CPU for long periods
WordPress or application pages load slowly
CPU spikes at predictable times
Database process list shows many running queries
Admin dashboards or checkout pages time out

Common causes

Missing or unused indexes
Large table scans from plugins or reports
Too many concurrent connections
Cron tasks or backups running during traffic
Poorly optimised queries after an application update
Storage latency causing queries to pile up

Safe first checks

These checks are intended to help identify the direction of the issue. Always adjust paths, service names and commands for your environment.

Show running queries

mysqladmin processlist

Enable/check slow query log

mysql -e "SHOW VARIABLES LIKE 'slow_query_log'; SHOW VARIABLES LIKE 'long_query_time';"

Check CPU and I/O

top -o %CPU -b -n1 | head -20; iostat -xz 1 3

Review table sizes

mysql -e "SELECT table_schema, ROUND(SUM(data_length+index_length)/1024/1024) MB FROM information_schema.tables GROUP BY table_schema ORDER BY MB DESC;"

Typical fixes

Use slow query logs to find repeat offenders
Add or adjust indexes carefully
Reduce heavy plugin/reporting workload
Move maintenance jobs away from peak traffic
Tune connection and buffer settings to fit server resources
Investigate disk latency when CPU and I/O rise together

When to get help

Get help if the system is production-facing, customer data is involved, backups are uncertain, or the issue affects revenue, security or uptime. We can review the logs, confirm the cause and quote a fixed-scope fix where appropriate.

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