!!col

• Enable runtime prefetching of personalized content by including it in prefetch requests.
• Use use cache: private when you need to cache user-specific data that depends on cookies, headers, or search params.
• Unlike regular use cache, private caches can access request-specific APIs like cookies() and headers() directly inside the cached function.
• Private caches are never persisted to cache handlers - they're only used to mark the dynamic content as runtime prefetchable.
• Without use cache: private, personalized content cannot be prefetched and must wait until navigation occurs.

!!col

async function getRecommendations(productId: string) {
  // !mark
  'use cache: private';
  cacheTag(`recommendations-${productId}`);
  cacheLife({ stale: 60 });

  // Can call cookies() INSIDE the cached function!
  // !mark
  const sessionId = (await cookies()).get('session-id')?.value || 'guest';

  return getPersonalizedRecommendations(productId, sessionId);
}

async function Recommendations({ productId }: { productId: string }) {
  // This will be runtime prefetched automatically
  const recommendations = await getRecommendations(productId);

  return (
    <div>
      {recommendations.map((rec) => (
        <ProductCard key={rec.id} product={rec} />
      ))}
    </div>
  );
}

export const unstable_prefetch = {
  mode: 'runtime',
  samples: [
    { params: { id: '1' }, cookies: [{ name: 'session-id', value: '1' }] },
  ],
};