Indexing Strategies — Making Your Database Fast
Understand what indexes are, how B-trees work, when to index, and how composite indexes can dramatically speed up your queries.
15 min readdatabases, sql, indexing, performance, b-tree
Your query is correct. It returns the right data. But it takes 4 seconds on a table with a million rows. Your users are staring at a spinner. Your API is timing out.
The fix, almost every time, is an index.
Indexes are the single most impactful performance tool in your database toolkit. Understanding how they work — and when to use them — separates hobby databases from production-ready ones.
What Is an Index?
Think of an index like the index in the back of a textbook. If you want to find every mention of "PostgreSQL" in a 500-page book, you have two options:
- Full table scan: Read every page from start to finish. You'll find everything, but it takes a while.
- Index lookup: Flip to the index in the back, find "PostgreSQL," see that it's mentioned on pages 42, 107, and 3
This lesson is part of the Guild Member curriculum. Plans start at $29/mo.