Mobile-API Backend

Supabase is the core: Postgres + Row-Level Security + auth + storage + realtime, all behind a REST/GraphQL API the mobile client can call directly. Vercel (or Cloudflare Workers) hosts any custom edge functions you need beyond what Supabase exposes — webhook receivers, third-party API proxies, push-notification fan-out. Resend handles transactional email (verification, password reset, receipts). The trade-off vs. Firebase is that you get real Postgres instead of Firestore — joins, transactions, SQL — at the cost of a slightly less polished mobile SDK. The trade-off vs. rolling your own on Fly.io is everything: you skip writing auth, skip writing the API layer, skip ops. For a mobile app where the backend is a means to an end, this is the lowest-overhead path that doesn't lock you into a NoSQL document model.