The App Router enables React Server Components (RSC), which significantly reduce client-side JavaScript by rendering components on the server. This leads to faster initial loads, improved SEO through better metadata handling, and a simpler data-fetching model that eliminates the need for complex useEffect hooks for initial data.

We favor 'Server-First' state management. Use URL params for filterable state (search, pagination), React Server Components for server-side data, and lightweight atomic libraries like Zustand or Jotai only for truly interactive client-side UI states or complex global modals.

Rust-based tools like Turbopack, Biome, and Rolldown are drastically reducing build and lint times, often by 10x or more. This improves developer experience (DX) and shortens the feedback loop, which is critical for maintaining velocity in large mono-repo environments.

Focus on three key pillars: LCP (Largest Contentful Paint) via image optimization and pre-rendering, CLS (Cumulative Layout Shift) by reserving space for dynamic content, and INP (Interaction to Next Paint) by keeping the main thread clear through code-splitting and efficient event handlers.