Have you ever worked with a query plan in a database (EXPLAIN/EXPLAIN ANALYZE)?

Yes, I have worked with query plans in databases using EXPLAIN and EXPLAIN ANALYZE commands. These tools help understand how the DBMS executes a query: which indexes are used, the order of operations, cost estimates, and the number of rows at each step.

For example, in PostgreSQL, EXPLAIN shows the execution plan, and EXPLAIN ANALYZE additionally executes the query and shows actual costs and time. This helps identify bottlenecks and optimize queries, for instance, by adding indexes or rewriting the query.

Example usage:

EXPLAIN ANALYZE SELECT * FROM users WHERE email = 'example@example.com';

The result will show whether an index on email was used, how many rows were processed, and how long the execution took.