Why the App Router Changes Everything
Next.js 14's App Router represents a paradigm shift in how we build React applications. With React Server Components at its core, it fundamentally changes the performance characteristics of web applications.
Server Components vs Client Components
The key mental model: Server Components render on the server and send HTML — no JavaScript bundle. Client Components hydrate on the client. The rule: start with Server Components, opt into Client Components only when you need interactivity, browser APIs, or React hooks.
Data Fetching Patterns
In the App Router, data fetching happens in Server Components using async/await directly. Parallel fetching with Promise.all eliminates request waterfalls. The fetch API is extended to support caching and revalidation strategies.
Streaming and Suspense
Streaming with Suspense boundaries allows progressive rendering — users see meaningful content instantly while slower data fetches complete in the background. This is a massive improvement for data-heavy dashboards.