Senior Team for Realtime Web App

We are looking for an elite development team or highly experienced senior engineers to build the core of a production-grade realtime web application. The main benchmark for the user experience is "Whats App Web": extremely fast, responsive and reliable, with no noticeable lag, UI freezes or unnecessary loading states. This is not primarily a design project. Our priority is the underlying technology, performance, realtime architecture and reliability. Core functionality * Real-time 1:1 messaging * Message delivery/read status * Online/offline presence * Typing indicators * Image and video messaging * Fast media uploads * Voice/video calling using WebRTC * Push notifications * Mobile-first experience (especially iPhone/Safari) * Excellent desktop experience * PWA support * Offline caching / fast startup * Reliable reconnect and synchronization * Large conversation histories without UI slowdown * Production-grade security and scalability Technical expectations Strong practical experience with: * React + TypeScript or an equally strong modern web stack * WebSockets / realtime systems * WebRTC * IndexedDB / client-side data persistence * Service Workers / PWA * Performance optimization * PostgreSQL and Redis * Media upload / processing / CDN architecture * Automated testing * Production deployment and monitoring We prefer engineers who have already built real production systems, not simply prototypes or tutorial projects. What we need from applicants Please provide: 1. Your strongest relevant production project. 2. A live demo or publicly verifiable reference whenever possible. 3. Your exact role in that project. 4. Approximate scale: users, concurrent users, messages, video calls or traffic. 5. Which realtime architecture you used and why. 6. How you solved offline/reconnect, message ordering and duplicate-message problems. 7. How you handled performance on mobile Safari. 8. Your proposed architecture for this project. 9. Team size and the seniority of the actual engineers who would work on it. Please do not send generic agency portfolios. We are looking for a technically exceptional team with demonstrable realtime/web/mobile experience.