GitHub Pages gzips for us, so the deployed site never had this problem. The
Docker image serves through serve.ts, which did not — so a self-hoster shipped
the bundle at 344 KB where the site sends 100 KB, and the feed at 90 KB where
the site sends 10 KB. Roughly three times the bytes, and on anything slower than
a laptop on wifi three times the download.
Negotiated on `accept-encoding` and applied only to the text types this app
serves; a PNG is left alone rather than spending CPU to grow it. `Vary` goes out
on both answers, because a shared cache that does not know the response depends
on the request header will hand gzipped bytes to a client that never asked.
The compressed bytes are cached in memory and keyed by mtime — these files
change only on deploy, so re-gzipping 344 KB per request is waste, and keying on
mtime rather than holding forever keeps `bun run dev` serving what was just
rebuilt. A failure to compress falls through to the raw file: this is an
optimisation and never a reason to fail a request.
Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
