When we rebuilt Bloom Commerce, the old store took 6.8 seconds to become usable on a mid-range phone. Here is where those seconds went.
The biggest wins came from responsive images in AVIF, self-hosted fonts with font-display: swap, and loading three marketing scripts only after the first interaction.
None of this was clever engineering. It was measuring first, then removing what users never needed in the first place.
Barış Sezer