Uploaded February 2026 | Updated September 2026, 2 days ago
How do you measure performance when migrating to React Native without rebuilding your app from scratch?
At React Universe x Zalando Meetup in Berlin, Mohit Karekar (Principal Engineer at Zalando) walks through the challenges of measuring performance in a brownfield React Native setup.
Instead of replacing a native app with a greenfield build, Zalando introduced React Native incrementally. While the UI remained the same, the rendering model changed: from a single GraphQL response to a streaming, module-based architecture powered by an internal Rendering Engine.
In this talk, Mohit explains:
Why traditional screen load metrics were no longer enough
How Zalando defined a “Meaningful Render” metric inspired by LCP
How modules declare themselves as meaningful
How onLayout, custom performance marks, and OpenTelemetry spans power the measurement
What they learned during gradual rollouts in production
If you’re working on a brownfield React Native migration, performance observability, or incremental rollouts in large-scale apps, this session offers a concrete, production-tested approach.
Follow Callstack on X 🐦 https://x.com/callstackio
How do you measure performance when migrating to React Native without rebuilding your app from scratch?
At React Universe x Zalando Meetup in Berlin, Mohit Karekar (Principal Engineer at Zalando) walks through the challenges of measuring performance in a brownfield React Native setup.
Instead of replacing a native app with a greenfield build, Zalando introduced React Native incrementally. While the UI remained the same, the rendering model changed: from a single GraphQL response to a streaming, module-based architecture powered by an internal Rendering Engine.
In this talk, Mohit explains:
Why traditional screen load metrics were no longer enough
How Zalando defined a “Meaningful Render” metric inspired by LCP
How modules declare themselves as meaningful
How onLayout, custom performance marks, and OpenTelemetry spans power the measurement
What they learned during gradual rollouts in production
If you’re working on a brownfield React Native migration, performance observability, or incremental rollouts in large-scale apps, this session offers a concrete, production-tested approach.
Follow Callstack on X 🐦 https://x.com/callstackio
