Next.js 14 Caching Explained: All Four Layers and When to Use Each

The Caching Hierarchy

Next.js 14 has four caching layers. Most developers use one and wonder why their app is slow -- or why their data is stale.

Understanding all four lets you cache aggressively where it's safe and invalidate precisely where it's needed.

Layer 1: Request Memoization

Within a single render, identical fetch calls are deduplicated automatically:

// These two calls in different components = ONE network request
// app/layout.tsx
const user = await fetch('/api/user/me')

// app/dashboard/page.tsx
const user = await fetch('/api/user/me') // Served from React cache

// To opt out (rare):
const user = await fetch('/api/user/me', { cache: 'no-store' })

Layer 2: Data Cache

Server-side persistent cache across requests and deploys:

// Cache forever (until manually revalidated)
const products = await fetch('https://api.example.com/products', {
  cache: 'force-cache' // Default for fetch in Server Components
})

// Cache for 60 seconds
const prices = await fetch('https://api.example.com/prices', {
  next: { revalidate: 60 }
})

// Never cache (always fresh)
const liveData = await fetch('https://api.example.com/live', {
  cache: 'no-store'
})

// Tag for targeted invalidation
const post = await fetch(`https://api.example.com/posts/${id}`, {
  next: { tags: [`post-${id}`, 'posts'] }
})

Layer 3: Full Route Cache

Static pages are cached at build time or on first request:

// app/blog/[slug]/page.tsx

// Static: pre-rendered at build time
export async function generateStaticParams() {
  const posts = await db.post.findMany()
  return posts.map(p => ({ slug: p.slug }))
}

// Force dynamic: opt out of static rendering
export const dynamic = 'force-dynamic'

// ISR: revalidate every N seconds
export const revalidate = 3600 // 1 hour

Layer 4: Router Cache (Client-Side)

Prefetched route segments cached in the browser:

// Prefetch on hover (default for <Link>)
<Link href="/products" prefetch={true}>
  Products
</Link>

// Disable prefetch
<Link href="/admin" prefetch={false}>
  Admin
</Link>

// Programmatic invalidation
import { useRouter } from 'next/navigation'
const router = useRouter()
router.refresh() // Clears client-side cache for current page

Cache Invalidation Strategies

// Server Action: revalidate after mutation
'use server'

import { revalidatePath, revalidateTag } from 'next/cache'

export async function updatePost(id: string, data: UpdatePostData) {
  await db.post.update({ where: { id }, data })

  revalidatePath(`/blog/${data.slug}`)  // Specific page
  revalidatePath('/blog')               // Listing page
  revalidateTag(`post-${id}`)           // All fetch calls tagged with this
}

// Webhook-triggered invalidation
// app/api/revalidate/route.ts
export async function POST(req: Request) {
  const { secret, tag, path } = await req.json()

  if (secret !== process.env.REVALIDATION_SECRET) {
    return Response.json({ error: 'Unauthorized' }, { status: 401 })
  }

  if (tag) revalidateTag(tag)
  if (path) revalidatePath(path)

  return Response.json({ revalidated: true })
}

When to Use Each

User-specific data (dashboard, profile):
  -> cache: 'no-store' or dynamic = 'force-dynamic'

Public content that changes hourly (blog, docs):
  -> revalidate: 3600

Public content that changes on publish (CMS):
  -> cache: 'force-cache' + revalidateTag() on publish webhook

Real-time data (prices, inventory):
  -> cache: 'no-store' + client-side polling or WebSocket

Static marketing pages:
  -> generateStaticParams() + revalidate: false (build-time only)

Database Query Caching with unstable_cache

import { unstable_cache } from 'next/cache'

// Cache a DB query like a fetch call
const getCachedProducts = unstable_cache(
  async () => db.product.findMany({ where: { active: true } }),
  ['active-products'],
  { revalidate: 300, tags: ['products'] } // 5 minutes
)

// In a Server Component:
const products = await getCachedProducts()

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