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Caching and Revalidation

In Next.js 16 caching is explicit. With Cache Components you mark work with "use cache", give it a lifetime with cacheLife, tag it with cacheTag, and invalidate it with updateTag, revalidateTag or revalidatePath. Know which layer you are touching: render-pass memoization, the server cache, prerendered HTML, or the client router.

Key points

1
Caching is opt-in. A plain fetch is not stored in the persistent cache; identical GET fetches are only memoized for one render pass (not in Route Handlers).
2
"use cache" needs cacheComponents: true. Its key is the build ID, a function ID and the serialized arguments, with captured closure variables bound as arguments.
3
Cached scopes cannot read cookies(), headers() or searchParams. Read them outside and pass the value in, or use "use cache: private", which only caches per request and in the browser.
4
cacheLife: stale is the client router window (minimum 30 s), revalidate triggers background regeneration, and expire is the point after which a request waits. Without a cacheLife call, default applies (5 m / 15 m / never).
5
updateTag is for read-your-own-writes and only works in Server Actions. revalidateTag(tag, profile) serves stale content while revalidating, and { expire: 0 } is the immediate option for webhooks.
6
Default runtime entries live in per-instance memory. Serverless rarely reuses them, so use "use cache: remote" with a cacheHandlers backend to share them. No "use cache" entry survives a new deploy.
7
On multi-instance self-hosting, revalidation is local unless the cache handler syncs tags through updateTags() and refreshTags().

Common traps

revalidatePath("/blog") does not refresh other pages that share the same tagged data, and with rewrites you must pass the destination path.
unstable_cache keys do not include closure variables. Leave the user ID out of the key and every user is served the first user's data.
A short-lived cache (seconds, revalidate: 0, or expire under 5 minutes) nested in a "use cache" scope with no explicit cacheLife fails the build. Always set an explicit lifetime.

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Test yourself on Caching and Revalidation

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