The database queries started executing slowly. What is the sequence of actions to troubleshoot the problem?

The following procedure is recommended for troubleshooting slow database queries:

1. Identify problematic queries — use logs or database monitoring to determine which queries are running slowly.
2. Check query execution plans (EXPLAIN) — analyze how the DBMS executes queries, whether there are full table scans, missing indexes.
3. Check indexes — ensure that there are appropriate indexes for frequently used conditions and joins.
4. Assess server load — check CPU load, memory usage, disk, network to rule out hardware issues.
5. Check statistics and their relevance — outdated statistics can lead to inefficient execution plans.
6. Look at locks and contention — queries might be waiting for resources to be released.
7. Optimize queries — rewrite or break down complex queries, use caching.
8. Conduct load testing — to understand how the system behaves under load.

This systematic approach will help identify and eliminate the causes of slowdown.