Loading Time Matters
Article Summary
Zalando proved that every 100ms of loading time equals real money: a 0.7% revenue lift per session. When 75% of your traffic is mobile, milliseconds become millions.
Zalando's engineering team set out to improve site performance by 20% over five months. They exceeded their goal with a 25% improvement by systematically attacking loading time from multiple angles, from framework upgrades to dependency cleanup.
Key Takeaways
- Upgrading React 15.6 to 16.2 saved over 100ms in JavaScript execution
- Replaced react-lazyload with LQIP to eliminate two major mobile reflows
- webpack-bundle-analyzer plus tree-shaking cut Header Fragment by 25% (9KB gzipped)
- SVG precision optimization slashed image sizes by roughly 50%
- Removing unused JSON props from SSR reduced page weight by 17KB
Zalando achieved 25% faster loading times in five months, translating directly to measurable revenue gains on mobile-dominant traffic.
About This Article
Zalando's mobile traffic, which made up over 75% of their usage, was slowing down because lazy-loading libraries like react-lazyload and unused react-virtualized components were causing unnecessary DOM reflows.
The team switched from react-lazyload to Low Quality Image Placeholders (LQIP) on mobile and removed the unused react-virtualized components. This eliminated the reflow bottlenecks across both platforms.
The reflow fixes helped deliver a 25% improvement in loading times overall. For their mobile-focused user base, this translated directly into measurable revenue gains.