Scaling React Native at Zalando: How Brownfield Migration Paid Off

Zalando wanted to improve delivery speed and let teams build across platforms. Its existing Rendering Engine, a React framework already used on the web, offered reusable features such as data fetching and feature toggles. The team also considered Kotlin Multiplatform and native apps, but valued React Native’s fit with its existing React skills and framework.

Zalando’s native apps had been in development for more than 10 years, so the team prepared research, documented tradeoffs, and used a proof of concept to make the case. The proof of concept took 1.5 full-time engineers over 15 days and demonstrated multiple screens with real data and observability. A brownfield rollout let Zalando test selected screens and traffic gradually, rather than replace the app all at once.

The first screen was chosen for low risk and low traffic, with feature toggles available to disable it if needed. Later screens tested demanding cases such as image and video content and long, scrolling lists. Zalando created a “meaningful render” metric for the time until key content appears, compared React Native screens with native versions, and checked business metrics through staged rollouts and A/B tests.

To keep the migration isolated from existing app dependencies, Zalando packaged React Native as a library consumed through native interfaces: an XCFramework on iOS and an AAR on Android. Dependency injection lets the host app provide services such as wishlist, cart, and authentication, avoiding duplicate implementations. The team also distributed a prebuilt app that connects to a local Metro bundler to make development easier.

The team reported around four screens fully rolled out, 12 in testing or monitoring, and seven code complete. Native engineers learned React Native and shipped important screens, including the home screen. Zalando aimed to bring around 90% of app traffic to React Native by early 2026, while focusing next on technical debt, observability, list performance, web interoperability, and community contributions.