How I Built a Credit Card Rewards Optimizer with React Native, Supabase, and Stripe in 2 Weeks

Two weeks. One idea. 410 credit cards. A working subscription app with AI built in. This is the technical story of how I built Rewardly — a credit card rewards optimizer for Canadians — from zero to production, solo, in 14 days. The Problem I Was Solving Canadians have some of the best credit card rewards programs in the world. But the comparison tools are terrible. Most sites are US-first, affiliate-stuffed, and tell you nothing useful about your specific spending patterns. The real question isn't "what's the best credit card?" It's: given how I actually spend money, which card — or combination of cards — maximizes my rewards? That's a data problem. I knew I could build something better. Tech Stack (Made in 10 Minutes) React Native + Expo — cross-platform from day one, web included Supabase — Postgres, auth, edge functions, RLS, all in one Stripe — payments, no thinking required Vercel — deploy on push Claude Haiku — the AI advisor ("Sage") No custom backend. Just Supabase edge functi