react-server-components

React Server Components

Build performant applications with React Server Components and Next.js App Router.

Core Workflow

Understand RSC model: Server vs client components
Design component tree: Plan server/client boundaries
Implement data fetching: Fetch in server components
Add interactivity: Client components where needed
Enable streaming: Suspense for progressive loading
Optimize: Minimize client bundle size

Server vs Client Components

Key Differences

Feature Server Components Client Components

Rendering Server only Server + Client

Bundle size Zero JS sent Adds to bundle

Data fetching Direct DB/API access useEffect/TanStack Query

State/Effects No hooks Full React hooks

Event handlers No Yes

Browser APIs No Yes

File directive Default (none) 'use client'

When to Use Each

Server Components (Default)

Static content
Data fetching
Backend resource access
Large dependencies (markdown, syntax highlighting)
Sensitive logic/tokens

Client Components

Interactive UI (onClick, onChange)
useState, useEffect, useReducer
Browser APIs (localStorage, geolocation)
Custom hooks with state
Third-party client libraries

Basic Patterns

Server Component (Default)

// app/users/page.tsx (Server Component - no directive needed) import { db } from '@/lib/db';

async function getUsers() { return db.user.findMany({ orderBy: { createdAt: 'desc' }, }); }

export default async function UsersPage() { const users = await getUsers();

return ( <div> <h1>Users</h1> <ul> {users.map((user) => ( <li key={user.id}>{user.name}</li> ))} </ul> </div> ); }

Client Component

// components/Counter.tsx 'use client';

import { useState } from 'react';

export function Counter() { const [count, setCount] = useState(0);

return ( <button onClick={() => setCount(count + 1)}> Count: {count} </button> ); }

Composition Pattern

// app/dashboard/page.tsx (Server Component) import { db } from '@/lib/db'; import { DashboardClient } from './DashboardClient'; import { StatsCard } from '@/components/StatsCard';

async function getStats() { const [users, orders, revenue] = await Promise.all([ db.user.count(), db.order.count(), db.order.aggregate({ _sum: { total: true } }), ]); return { users, orders, revenue: revenue._sum.total }; }

export default async function DashboardPage() { const stats = await getStats();

return ( <div> {/* Server-rendered static content */} <h1>Dashboard</h1>

  {/* Server components with data */}
  &#x3C;div className="grid grid-cols-3 gap-4">
    &#x3C;StatsCard title="Users" value={stats.users} />
    &#x3C;StatsCard title="Orders" value={stats.orders} />
    &#x3C;StatsCard title="Revenue" value={`$${stats.revenue}`} />
  &#x3C;/div>

  {/* Client component for interactivity */}
  &#x3C;DashboardClient initialData={stats} />
&#x3C;/div>

); }

// app/dashboard/DashboardClient.tsx 'use client';

import { useState } from 'react'; import { DateRangePicker } from '@/components/DateRangePicker'; import { Chart } from '@/components/Chart';

interface DashboardClientProps { initialData: Stats; }

export function DashboardClient({ initialData }: DashboardClientProps) { const [dateRange, setDateRange] = useState({ from: null, to: null });

return ( <div> <DateRangePicker value={dateRange} onChange={setDateRange} /> <Chart data={initialData} /> </div> ); }

Data Fetching Patterns

Parallel Data Fetching

// app/page.tsx async function getUser(id: string) { const res = await fetch(/api/users/${id}); return res.json(); }

async function getPosts(userId: string) { const res = await fetch(/api/users/${userId}/posts); return res.json(); }

async function getComments(userId: string) { const res = await fetch(/api/users/${userId}/comments); return res.json(); }

export default async function ProfilePage({ params }: { params: { id: string } }) { // Parallel fetching - all requests start simultaneously const [user, posts, comments] = await Promise.all([ getUser(params.id), getPosts(params.id), getComments(params.id), ]);

return ( <div> <UserHeader user={user} /> <PostsList posts={posts} /> <CommentsList comments={comments} /> </div> ); }

Sequential Data Fetching (When Dependent)

export default async function OrderPage({ params }: { params: { id: string } }) { // Sequential - second fetch depends on first const order = await getOrder(params.id); const customer = await getCustomer(order.customerId);

return ( <div> <OrderDetails order={order} /> <CustomerInfo customer={customer} /> </div> ); }

Caching and Revalidation

// Static data (cached indefinitely) async function getStaticData() { const res = await fetch('https://api.example.com/static', { cache: 'force-cache', // Default }); return res.json(); }

// Dynamic data (no cache) async function getDynamicData() { const res = await fetch('https://api.example.com/dynamic', { cache: 'no-store', }); return res.json(); }

// Revalidate after time async function getRevalidatedData() { const res = await fetch('https://api.example.com/data', { next: { revalidate: 3600 }, // Revalidate every hour }); return res.json(); }

// Revalidate by tag async function getTaggedData() { const res = await fetch('https://api.example.com/products', { next: { tags: ['products'] }, }); return res.json(); }

// Trigger revalidation import { revalidateTag } from 'next/cache'; revalidateTag('products');

Streaming with Suspense

Page-Level Streaming

// app/dashboard/page.tsx import { Suspense } from 'react'; import { StatsCards, StatsCardsSkeleton } from './StatsCards'; import { RecentOrders, RecentOrdersSkeleton } from './RecentOrders'; import { TopProducts, TopProductsSkeleton } from './TopProducts';

export default function DashboardPage() { return ( <div> <h1>Dashboard</h1>

  {/* Each section streams independently */}
  &#x3C;Suspense fallback={&#x3C;StatsCardsSkeleton />}>
    &#x3C;StatsCards />
  &#x3C;/Suspense>

  &#x3C;div className="grid grid-cols-2 gap-4 mt-8">
    &#x3C;Suspense fallback={&#x3C;RecentOrdersSkeleton />}>
      &#x3C;RecentOrders />
    &#x3C;/Suspense>

    &#x3C;Suspense fallback={&#x3C;TopProductsSkeleton />}>
      &#x3C;TopProducts />
    &#x3C;/Suspense>
  &#x3C;/div>
&#x3C;/div>

); }

Component with Data

// app/dashboard/StatsCards.tsx import { db } from '@/lib/db';

async function getStats() { // Simulate slow query await new Promise((resolve) => setTimeout(resolve, 2000)); return db.stats.findFirst(); }

export async function StatsCards() { const stats = await getStats();

return ( <div className="grid grid-cols-4 gap-4"> <Card title="Revenue" value={stats.revenue} /> <Card title="Orders" value={stats.orders} /> <Card title="Customers" value={stats.customers} /> <Card title="Products" value={stats.products} /> </div> ); }

export function StatsCardsSkeleton() { return ( <div className="grid grid-cols-4 gap-4"> {[...Array(4)].map((_, i) => ( <div key={i} className="h-24 bg-gray-200 animate-pulse rounded" /> ))} </div> ); }

Loading States

// app/products/loading.tsx export default function ProductsLoading() { return ( <div className="grid grid-cols-3 gap-4"> {[...Array(9)].map((_, i) => ( <div key={i} className="h-64 bg-gray-200 animate-pulse rounded" /> ))} </div> ); }

Server Actions

Form Actions

// app/contact/page.tsx import { submitContact } from './actions';

export default function ContactPage() { return ( <form action={submitContact}> <input name="email" type="email" required /> <textarea name="message" required /> <button type="submit">Send</button> </form> ); }

// app/contact/actions.ts 'use server';

import { z } from 'zod'; import { revalidatePath } from 'next/cache';

const schema = z.object({ email: z.string().email(), message: z.string().min(10), });

export async function submitContact(formData: FormData) { const validatedFields = schema.safeParse({ email: formData.get('email'), message: formData.get('message'), });

if (!validatedFields.success) { return { error: validatedFields.error.flatten().fieldErrors }; }

await db.contact.create({ data: validatedFields.data, });

revalidatePath('/contacts'); return { success: true }; }

With useActionState

// components/ContactForm.tsx 'use client';

import { useActionState } from 'react'; import { submitContact } from '@/app/contact/actions';

export function ContactForm() { const [state, formAction, isPending] = useActionState(submitContact, null);

return ( <form action={formAction}> <input name="email" type="email" required /> {state?.error?.email && <p className="text-red-500">{state.error.email}</p>}

  &#x3C;textarea name="message" required />
  {state?.error?.message &#x26;&#x26; &#x3C;p className="text-red-500">{state.error.message}&#x3C;/p>}

  &#x3C;button type="submit" disabled={isPending}>
    {isPending ? 'Sending...' : 'Send'}
  &#x3C;/button>

  {state?.success &#x26;&#x26; &#x3C;p className="text-green-500">Message sent!&#x3C;/p>}
&#x3C;/form>

); }

Optimistic Updates

// components/LikeButton.tsx 'use client';

import { useOptimistic, useTransition } from 'react'; import { likePost } from '@/app/actions';

interface LikeButtonProps { postId: string; initialLikes: number; isLiked: boolean; }

export function LikeButton({ postId, initialLikes, isLiked }: LikeButtonProps) { const [isPending, startTransition] = useTransition(); const [optimisticState, addOptimistic] = useOptimistic( { likes: initialLikes, isLiked }, (state, newIsLiked: boolean) => ({ likes: newIsLiked ? state.likes + 1 : state.likes - 1, isLiked: newIsLiked, }) );

const handleClick = () => { startTransition(async () => { addOptimistic(!optimisticState.isLiked); await likePost(postId); }); };

return ( <button onClick={handleClick} disabled={isPending}> {optimisticState.isLiked ? '❤️' : '🤍'} {optimisticState.likes} </button> ); }

Patterns for Common Use Cases

Authentication Check

// app/dashboard/layout.tsx import { redirect } from 'next/navigation'; import { getSession } from '@/lib/auth';

export default async function DashboardLayout({ children, }: { children: React.ReactNode; }) { const session = await getSession();

if (!session) { redirect('/login'); }

return ( <div> <nav>Welcome, {session.user.name}</nav> {children} </div> ); }

Passing Server Data to Client

// app/products/[id]/page.tsx import { getProduct } from '@/lib/products'; import { ProductGallery } from './ProductGallery';

export default async function ProductPage({ params }: { params: { id: string } }) { const product = await getProduct(params.id);

return ( <div> <h1>{product.name}</h1> <p>{product.description}</p>

  {/* Pass serializable data to client component */}
  &#x3C;ProductGallery
    images={product.images}
    initialIndex={0}
  />
&#x3C;/div>

); }

Nested Client Components

// components/Modal.tsx 'use client';

import { createContext, useContext, useState } from 'react';

const ModalContext = createContext<{ open: boolean; setOpen: (open: boolean) => void; } | null>(null);

export function ModalProvider({ children }: { children: React.ReactNode }) { const [open, setOpen] = useState(false); return ( <ModalContext.Provider value={{ open, setOpen }}> {children} </ModalContext.Provider> ); }

export function useModal() { const context = useContext(ModalContext); if (!context) throw new Error('useModal must be used within ModalProvider'); return context; }

Best Practices

Start with Server Components: Default to server, add 'use client' only when needed
Push client boundaries down: Keep interactivity in leaf components
Parallel fetch data: Use Promise.all for independent data
Use Suspense for streaming: Progressive loading for better UX
Colocate data fetching: Fetch where data is used
Minimize client bundle: Heavy libraries stay on server
Cache appropriately: Use revalidation strategies
Handle errors: Use error.tsx boundaries

Output Checklist

Every RSC implementation should include:

Server components for data fetching
'use client' only where needed
Suspense boundaries for streaming
Loading skeletons for each section
Parallel data fetching with Promise.all
Server actions for mutations
Proper caching strategy
Error boundaries (error.tsx)
Authentication checks in layouts
Minimal client JavaScript bundle

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