When is it appropriate to apply indexing in a database to improve performance?

Indexing in a database is advisable when:

• Queries with search conditions on specific columns are frequently executed (e.g., WHERE, JOIN, ORDER BY).
• The table contains a large number of records, and searches become slow without indexes.
• There is a need to speed up data retrieval, especially during frequent reads.

However, indexes occupy additional space and slow down insert, update, and delete operations, so they should not be created unnecessarily. It is optimal to index columns that are frequently used for filtering or sorting, but not all columns indiscriminately.

Example: if you have a users table with an email field, and you often search for users by email, it is advisable to create an index on this field.