A full-featured Android travel planning app that helps users organize every aspect of their trips - itineraries, expenses, packing lists, and AI-powered activity suggestions. Key achievements: - Built a monorepo with three independent services: Expo/React Native mobile app, Node.js/Express REST API, and a Python FastAPI AI microservice - Implemented offline-first architecture using React Query with AsyncStorage persistence, optimistic UI updates, and a Pro-tier offline mutation queue with automatic sync on reconnect - Integrated LangChain + OpenAI for activity suggestions, event scheduling optimization, budget prediction, and Gmail event import - Designed a tiered subscription system with RevenueCat SDK and server-side usage tracking, enforcing limits across free and Pro plans - Added multi-currency expense tracking, push notifications, Google Sign-In, and JWT auth with token refresh on reconnection