E-commerce Killing the Bundle that Was Killing Conversions

React 19 + Next. js 15 · Production Refactor

The Challenge: 2.4MB JS checkout on mobile - B

However, a mid-market e-commerce team saw that their mobile checkout completion rate was 31% below that of desktop. Digging into session replay highlighted a reproducible 2.1-second JavaScript parse delay on most mid-tier Android devices — the delay was incurred before a single pixel of checkout UI was visible.

Their Next. Loading full product catalog & admin SDK to every page in js 14 codebase. It was neither a clever…