Why do we need database monitoring?

Database monitoring exists to track its state and operation - catching problems before they cause failures or data loss.

It helps an administrator see:

1. Server load. How many connections, how much memory and CPU are being used.
2. Query performance. Which queries are "dragging down" the system.
3. Errors and failures. Failed connection attempts, transaction errors, overflowing logs.
4. Disk space usage. To free up or expand storage in time.
5. The state of replication and backups. To confirm the copies are actually working correctly.

Example tools: pgAdmin, Zabbix, Prometheus, MySQL Workbench, Grafana.

Summary: monitoring exists to keep the database running stably, quickly, and without surprises, and to let the administrator learn about a problem before users notice it.