Next.js Expert — Series 3

Preview — 3 of 10 questions

What does "use cache" do here, and how do cacheTag / cacheLife relate to it?

javascript

async function getCatalog(region: string) {
  'use cache';
  cacheTag('catalog');
  cacheLife('hours');
  return db.products.findMany({ where: { region } });
}

AIt marks the function as cacheable — Next.js caches the return value keyed by the function's serializable arguments (region), cacheLife('hours') sets the revalidation profile, and cacheTag('catalog') attaches a tag so revalidateTag('catalog') can purge it

BIt forces the function to run on the Edge runtime

CIt disables caching for the function, overriding the default

DIt is an alias for React.cache() and only dedupes within one render

With the dynamicIO experimental flag enabled, this page errors at build unless changed. What is the model?

javascript

export default async function Page() {
  const user = await getUser();        // uncached, per-request
  return <Profile user={user} />;
}

AdynamicIO disables all data fetching in Server Components

BUnder dynamicIO, any uncached async data access must be wrapped in <Suspense> (or live inside a "use cache" boundary). Data is either explicitly cached, or explicitly dynamic-behind-Suspense — there is no implicit "the whole route just becomes dynamic" fallback

CdynamicIO makes every route fully static and ignores cookies()

DIt only affects Route Handlers, not pages

Which props are valid to pass from a Server Component to a Client Component?

javascript

// Server Component
<ClientChart
  data={rows}
  formatter={(n) => n.toFixed(2)}
  onLoad={handleLoad}
  createdAt={new Date()}
/>

AAll of them — Next.js serializes anything

BOnly strings and numbers; objects and arrays throw

Cdata (plain serializable values), createdAt (a Date, which the RSC serializer supports along with Map, Set, BigInt, typed arrays, and Promises) are fine; formatter and onLoad are functions and throw — the only functions that may cross are Server Actions (functions marked "use server")

DFunctions are fine but Date objects are not

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