How do you create an index in PostgreSQL?

Create with CREATE INDEX. Basic: CREATE INDEX idx_name ON tablename(column);. Multi-column: CREATE INDEX idx_name ON tablename(col1, col2);. Unique index: CREATE UNIQUE INDEX idx_name ON tablename(column);. Partial index: CREATE INDEX idx_active_users ON users(email) WHERE is_active = true;. Expression index: CREATE INDEX idx_lower_email ON users(LOWER(email));. Concurrent creation (no table lock): CREATE INDEX CONCURRENTLY idx_name ON tablename(column); — takes longer but doesn't block reads/writes. Drop: DROP INDEX idx_name;. Rename: ALTER INDEX old_name RENAME TO new_name;. Always use CONCURRENTLY in production to avoid locking.