Error: cache() was called outside of a request during render (React Server Components)

What causes this error

Unlike a module-level memoization cache that lives for the process lifetime, React's cache() for Server Components is scoped to a single request/render — its whole purpose is deduplicating repeated calls to the same data-fetching function within one render pass, not caching across requests. `cacheSignal()` lets code detect when that lifetime has ended; calling into a cached function after that point, or from outside any request context at all, throws.

The Fix

import { cache } from 'react';

const getUser = cache(async (id: string) => {
  return db.user.findUnique({ where: { id } });
});

// Correct — called during a request's render, from a Server Component
async function ProfilePage({ params }) {
  const { id } = await params;
  const user = await getUser(id); // deduplicated with any other getUser(id) calls this request
  return <Profile user={user} />;
}

// Wrong — calling it at module scope, outside any request
const cachedUser = await getUser('123'); // throws — no active request

Common causes / variations

• Calling a `cache()`-wrapped function at module top-level instead of inside a component/render function
• Awaiting a cached call inside a background job or a `setTimeout` that outlives the originating request
• Confusing per-request `cache()` with a persistent cross-request cache (use a real cache store, e.g. Redis, for that)

Related errors

See also: Only plain objects can be passed to Client Components, dynamic server usage cookies.