How Zalando Loads Time Matters
Original post 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.
Continue reading
What This Article Covers
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.
This page summarizes “Loading Time Matters” by Zalando, published Jun 11, 2018. All credit for the original work goes to the authors.
