Database Indexes: How They Work and their Main Types

Data Engineering Concepts · Sep 23, 2026 · 24m

Database indexes are one of the most important tools for improving query performance - but there are many different types, and the differences between them are not always obvious.

In this episode, I explain how indexes work, what's their benefits and drawbacks, and I go through the main index types and concepts: B-tree and B+ tree indexes, dense and sparse indexes, bitmap and hash indexes, clustered and non-clustered indexes, composite and covering indexes, as well as duplicate and redundant indexes.

There also details about why column order matters in composite indexes and how an index-only…