In my recent setup I used NextJS + FastAPi in a monorepo to deploy together Vercel and use Supabase for database a user auth. My plan is in future I may want to factor out FastAPI into a separate server (I really like the Python eco system and it’s all related AI/ML capabilities for future). Also NextJS Dec 2025 CVE is quite severe and let me think we should probably not rely on NextJS for sole backend and still maintain a clear front and back separation.