I’m building a product that has two faces: a native Android app written in Kotlin and a web interface rendered with React JS. Both sides must evolve in lock-step, so I’m searching for one developer (or a tightly knit duo) who is equally at home in Android Studio and modern React/JavaScript tooling. Core scope The next milestone adds three cornerstone capabilities: • User authentication that shares a single credential pool across mobile and web. • Real-time updates so actions on one client instantly reflect on the other—think WebSockets or Firebase-style listeners. • Seamless payment integration supporting test and live environments. What you’ll hand over • Clean, well-commented Kotlin and React code pushed to our Git repo. • Build-ready project files plus instructions so my team can run both apps in one sitting. • A brief README outlining any third-party services or keys required. • Demo APK and a live React build that proves auth, live data flow, and payment work end-to-end. Acceptance checks 1. Sign-up, login, and token refresh succeed on first attempt on both platforms. 2. A test event created on Android appears on the web UI within two seconds (and vice versa). 3. Sandbox payments complete without errors and return correct callbacks. When you apply, focus on experience—especially projects where you delivered similar dual-stack features. Links to repos, stores, or demos speak louder than long proposals. I’m ready to start as soon as the right fit surfaces.