This session introduces Next.js 15, the first stable framework enabling the use of React 19 in production, with a focus on React Server Components adoption. The talk is split into two parts: separating a web page into server and client files, and then optimizing this separation for efficient component rendering.

In shared codebases, developers often face bugs in components they've never touched, created by people who have long left the company. How can one fix these bugs without breaking everything? This talk walks through a real-life case study: debugging a tricky autocomplete. From initial diagnosis to resolution, you'll learn practical debugging tips for legacy code, how to avoid common pitfalls, and how to move forward efficiently without starting from scratch.

Achieving fine-grained reactivity in a React application without compromising developer experience is a long-standing challenge. For real-time applications designed to display hundreds of millions of rows without perceptible latency, fine reactivity is crucial. This presentation explores how we efficiently ingested, displayed, and updated large datasets seamlessly, maintaining both developer and user experience.