Have you worked with indexes created under specific conditions in a database?

Yes, I have experience working with partial indexes, which are created with conditions (e.g., WHERE clause). They index only a subset of rows satisfying the condition, reducing index size and speeding up queries that filter on that condition.

Example in SQL:

CREATE INDEX idx_active_users ON users (last_login) WHERE is_active = true;

This index contains only active users, speeding up queries for active users.

In Java applications working with databases, such indexes can be used to optimize query performance via ORM or JDBC if the database supports partial indexes (e.g., PostgreSQL).

Using conditional indexes is an effective optimization technique, especially with large datasets and frequent filtering on specific attributes.