What actions would you take if database performance degrades?

When database performance deteriorates, the following steps should be taken:

1. Query profiling — check which queries take the longest to execute using logging or profiling tools (e.g., slow query log in MySQL).
2. Query optimization — rewrite inefficient queries, add necessary indexes, remove redundant JOINs or subqueries.
3. Caching — use caching for frequently requested data (e.g., Redis or built-in application cache).
4. Database configuration check — ensure that the database server settings are optimal (memory, connection pool).
5. Use connection pools — to avoid overhead on establishing connections.
6. Vertical or horizontal scaling — if the load is high, consider scaling the database.

Example: if a query to a table without an index takes a long time, adding an index on the necessary column can significantly speed up the retrieval.