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Database Indexing Strategies: B-Tree, Hash, GIN, GiST, and BRIN Explained

Adding an index is the highest-ROI database optimization — a well-chosen index can turn a 30-second sequential scan into a sub-millisecond index lookup. But indexing is full of trade-offs: each index slows writes, consumes storage, and requires the query planner to choose it. This guide covers index types, when to use each, and how to verify they are actually working.

Index Types: Complete Reference

Index Type How It Works Best For Limitations Database Support

B-Tree Balanced tree, sorted order =, <, >, BETWEEN, LIKE 'prefix%', ORDER BY, GROUP BY Slow on LIKE '%suffix' (no leading wildcard) All databases (default index type)

Hash Hash table, O(1) lookup = (equality only) No range queries, no ORDER BY, no partial key matches PostgreSQL, MySQL (Memory engine)

GIN (Generalized…