Most indexing advice is written as if a table had one size. In practice the same table moves through very different regimes: it starts with a few hundred rows in a new product, reaches millions within a year, and on a successful product ends up in the hundreds of millions or billions. The index set that served it well at one size quietly becomes wrong at the next, either because indexes stop fitting in memory or because they slow down every write for little read benefit. This guide follows one t...