Introduction Fixing N+1 queries with select_related / prefetch_related or selectinload (see the previous post ) gets you down to a small, sane number of queries per request. The next bottleneck is what each query costs once the table has millions of rows — and that is almost always about indexing. An index turns "scan every row" into "look it up directly." Skip it, and a query that's instant in development takes seconds once real data volume shows up in production. How...