There's a category of performance work where you profile, hypothesize, measure, and claw back milliseconds. And then there's the other kind: someone else rewrote the engine, and you just have to move over. The esbuild-based application builder is the second kind. New Angular apps have used it by default since v17; the interesting story is migrating an old app that grew up on webpack.

The headline from the app I migrated — five years old, thick with legacy — is blunt: cold production builds went from "start it and go do something else" to under a minute, and the dev server's incremental rebuilds dropped from double-digit seconds to fast enough that I stopped alt-tabbing. I did not optimize anything.…