Tobbe

We built a real-time system for Postgres→React sync using a `LISTEN/NOTIFY` Postgres trigger, GraphQL `@live` queries, a React hook and a custom ORM-inspired GraphQL query builder. Starting from ESP32 microcontroller devices sending MQTT messages and a Node/Postgres backend, we moved from polling to a stand-alone PoC with Yoga, Prisma triggers, and a custom `useLiveQuery` hook. After proving that the PoC was working we integrated with all our existing full-stack apps. So now we have low-latency UI updates, reusable cross-app logic, and easier extension for new sensor values. Great UX and excellent DX. TOC - Title & minimal intro - Goals (What We Needed) - Existing System (What We Had) - Attempts & Why They Failed - Solution Overview - Postgres `LISTEN/NOTIFY` - `useLiveQuery` React hook - Yoga and Apollo `@live` integration - GraphQL query builder - GraphQL SDL generator - GraphQL resolver generator - Demo / Results - Tradeoffs, Lessons & Next Steps - Q&A