nextjs-caching

name	nextjs-caching
description	The 4 layers of caching in Next.js. Use when configuring request memoization, data cache, full-route cache, or router cache in Next.js. (triggers: **/page.tsx, **/layout.tsx, **/action.ts, unstable_cache, revalidateTag, Router Cache, Data Cache)

Caching Architecture

Priority: P1 (HIGH)

Next.js has 4 distinct caching layers. Understanding them prevents stale data bugs.

Implementation Guidelines

• Next.js 15+ Standard: Use fetch with revalidate: number or cache: 'force-cache' for API calls. Use unstable_cache or the new 'use cache' (experimental) for custom data stores.
• Layers: Distinguish between Data Cache (persistent across requests) and Request Memoization (React's lifecycle specific). Use cache() from React to deduplicate fetches within a single render.
• Invalidation: Use revalidatePath('/') after mutations or revalidateTag('tag-name') for granular cache purging.
• Client Cache: Understand the Router Cache (in-memory on client) and its 30s-min lifespan. Clear it using router.refresh().
• Static Assets: Leverage generateStaticParams for pre-rendering static routes at build time. Use ISR (Incremental Static Regeneration) for content that updates periodically.
• Streaming: Combine Suspense with fetch triggers to prevent slow data from blocking the entire page render.
• Next.js 16+: Favor 'use cache' and cacheLife() over revalidate: number where available for deterministic caching.

Layer	Where	Control
Request Memoization	Server	React cache()
Data Cache	Server	'use cache', revalidateTag
Full Route Cache	Server	Static Prerendering
Router Cache	Client	router.refresh()

Implementation Details

See Cache Components & PPR for detailed key generation, closure constraints, and invalidation strategies.

Anti-Patterns

• No unstable_cache in Next.js 16+: Use 'use cache' directive with cacheLife() instead.
• No router.refresh() for server data: Prefer revalidateTag() for targeted cache busting.
• No caching user-specific data at route level: Wrap personal data in <Suspense> with 'use cache'.
• No long-lived cache without tags: Assign cacheTag() for fine-grained invalidation control.