nextjs-app-router-data-fetching

name	nextjs-app-router-data-fetching
version	1.0
description	Data fetching patterns for Next.js 14+ App Router including async Server Components and Server Actions. PROACTIVELY activate for: (1) fetching data in Server Components, (2) implementing Server Actions for mutations, (3) configuring caching and revalidation. Triggers: "fetch data", "server action", "revalidate"
group	foundation
core-integration	{"techniques":{"primary":["structured_decomposition"],"secondary":[]},"contracts":{"input":"none","output":"none"},"patterns":"none","rubrics":"none"}

Next.js App Router Data Fetching

Pattern 1: Async Server Components (Recommended)

// app/posts/page.tsx (Server Component)
export default async function PostsPage() {
  // Fetch directly in Server Component
  const posts = await fetch('https://api.example.com/posts', {
    next: { revalidate: 60 } // Revalidate every 60 seconds
  }).then(res => res.json());

  return (
    <div>
      {posts.map(post => (
        <article key={post.id}>{post.title}</article>
      ))}
    </div>
  );
}

Benefits:

• No loading spinners (rendered on server)
• No client-server waterfalls
• Can access database directly (no API layer needed)
• Automatic request deduplication

Pattern 2: Server Actions (For Mutations)

// app/actions/posts.ts
'use server'

import { revalidatePath } from 'next/cache';

export async function createPost(formData: FormData) {
  const title = formData.get('title');

  await db.post.create({ data: { title } });

  revalidatePath('/posts'); // Invalidate cache

  return { success: true };
}

// app/posts/new/page.tsx
import { createPost } from '@/app/actions/posts';

export default function NewPostPage() {
  return (
    <form action={createPost}>
      <input name="title" />
      <button type="submit">Create</button>
    </form>
  );
}

Caching Strategies

// No caching (always fresh)
fetch('...', { cache: 'no-store' })

// Cache forever (static)
fetch('...', { cache: 'force-cache' })

// Time-based revalidation (ISR)
fetch('...', { next: { revalidate: 3600 } }) // 1 hour

// On-demand revalidation (with tags)
fetch('...', { next: { tags: ['posts'] } })
// Later: revalidateTag('posts')

Anti-Pattern: useEffect for Data Fetching

// DON'T: Client-side fetching with useEffect
'use client'
function Posts() {
  const [posts, setPosts] = useState([]);

  useEffect(() => {
    fetch('/api/posts').then(r => r.json()).then(setPosts);
  }, []);

  return // ... causes client-server waterfall, loading spinner needed
}

// DO: Server Component
async function Posts() {
  const posts = await fetch('...').then(r => r.json());
  return // ... pre-rendered, no loading state
}

Parallel Data Fetching

export default async function Page() {
  // Fetch in parallel
  const [user, posts, comments] = await Promise.all([
    fetchUser(),
    fetchPosts(),
    fetchComments(),
  ]);

  return // ...
}

For database integration and advanced caching, see resources/database-patterns.md.