

Tomasz Żelawski
Software Engineer at Software Mansion

I'm Tomasz Żelawski, a software engineer working at Software Mansion, working in the React Native Open Source team for over two years. I utilize my deep love for low-level programming and academic aspects of code to manipulate abstract syntax trees, chase race conditions and basically hack whatever I can.
React Native Ecosystem: libraries, tooling, and who keeps it alive
The React Native ecosystem is more than just a framework. It is the people building the libraries, the tooling, and the invisible infrastructure that make modern mobile apps possible. This panel looks at the projects developers rely on every day, the challenges of keeping them maintained and evolving, and the community effort required to keep React Native moving forward. We’ll discuss what’s changing in the ecosystem, which tools are becoming essential, how maintainers decide where to invest their time, and what developers should know to build with confidence today and beyond.
The cost of JavaScript in React Native apps
React Native is a complex web of dependencies and environments that interact in ways often hidden from the developer. We happily build our components and native modules, but rarely see what actually happens under the hood when data crosses between worlds.
In this talk, I want to explore the overhead, missed optimizations, and boilerplate we generate every time our app is translated from JavaScript to native.
I'll cover the JavaScript Interface (JSI) and Java Native Interface (JNI), and share measurements such as how expensive it really is to pass a single integer from JavaScript into a native component.
I'll also look at related types like folly::dynamic and the new (still unstable) jsi::ISerialized fast serialization interface in Hermes.
Time permitting, I'll touch on the performance of native modules and discuss when it's actually better to keep something in JavaScript rather than handing it off to native.
