React Server Components

RSC + Next.js App Router patterns for streaming, caching, and minimal client JS.

RSC vs Client Components Decision Matrix

Use Server Component (default) when:
  - Fetching data from DB / API
  - Accessing backend resources (filesystem, secrets)
  - No interactivity (useState, useEffect, event listeners)
  - Heavy dependencies (no bundle cost)

Use Client Component ("use client") when:
  - useState / useReducer / useRef
  - useEffect / lifecycle hooks
  - Browser APIs (window, navigator, IntersectionObserver)
  - Event listeners (onClick, onChange)
  - Third-party client libraries (charts, drag-drop)