What indexes do you know and which ones have you used?

Main types of indexes I have worked with:

• B-Tree index — the most common, suitable for fast equality and range searches.
• Hash index — efficient for exact key lookups, but does not support range queries.
• Composite (multi-column) index — an index on multiple columns, speeds up complex queries filtering by several fields.
• Full-text index — for text searches, e.g., in PostgreSQL or MySQL.
• GIN/GiST indexes — specialized indexes for working with arrays, JSONB, and geospatial data (PostgreSQL).

In projects with Go, where I worked with databases, I most often used B-Tree and composite indexes to optimize queries. For example, in PostgreSQL, I created a composite index to speed up filtering by multiple columns:

CREATE INDEX idx_user_status_date ON users (status, created_at);

This significantly reduced query execution time with conditions on status and date.