Feed Caching & Staleness

A feed endpoint with no Cache-Control header or client-side staleTime triggers a full database query on every page visit, every back-navigation, and every tab focus. For a social feed, this means re-fetching 20 posts with author joins and like counts every few seconds per active user — a multiplier that kills database throughput under modest concurrent load. ISO 25010:2011 performance-efficiency requires that repeated reads of slowly-changing data not incur full round-trip costs each time. Without cache invalidation on post creation, you also risk serving stale feeds, but that is a secondary concern relative to the cost of zero caching.

Add a short stale-while-revalidate cache header to the feed API response, and configure staleTime on the client-side query so back-navigation reuses cached data rather than re-fetching.

// app/api/feed/route.ts
export async function GET(req: Request) {
  const feed = await getFeed(getCurrentUserId())

  return Response.json(feed, {
    headers: {
      'Cache-Control': 'private, max-age=30, stale-while-revalidate=120'
    }
  })
}

// hooks/useFeed.ts
export function useFeed() {
  return useQuery({
    queryKey: ['feed'],
    queryFn: () => fetch('/api/feed').then(r => r.json()),
    staleTime: 60 * 1000,    // treat data as fresh for 60s
    gcTime: 10 * 60 * 1000  // keep in cache for 10 min
  })
}

// After creating a post, invalidate so the new item appears
queryClient.invalidateQueries({ queryKey: ['feed'] })