What methods can you apply to improve the efficiency of query execution in a database as the number of users increases?

To improve the efficiency of database queries as the number of users grows, the following methods can be applied:

• Indexing: creating indexes on frequently used fields in WHERE, JOIN, and ORDER BY clauses.
• Query optimization: rewriting queries to reduce the number of operations, using only necessary fields (SELECT instead of SELECT *).
• Caching: caching query results at the application or database level.
• Pagination: loading data in parts to avoid system overload.
• Sharding and replication: distributing data across multiple servers to balance the load.
• Using prepared statements for recurring queries.
• Query profiling with EXPLAIN and other tools to identify bottlenecks.

Example of indexing in SQL:

CREATE INDEX idx_user_email ON users(email);

This speeds up user searches by email.