Serhii O.

🥇 𝐓𝐨𝐩 𝟏% 𝐓𝐚𝐥𝐞𝐧𝐭 - 𝐄𝐱𝐩𝐞𝐫𝐭 𝐕𝐞𝐭𝐭𝐞𝐝 on Upwork. I help startups and product teams build fast, clean, and scalable mobile apps. 👨‍💻 As a senior full stack developer with over 15 years of experience, I build apps that help startups and businesses grow. 🔧 𝐖𝐡𝐚𝐭 𝐈 𝐃𝐨 - Mobile Apps (iOS + Android): 40+ apps delivered. 25+ published to the App Store (⭐ 4.7 avg). Performance optimized, CI/CD deployed, built to scale. - IoT & BLE: Deep expertise with ESP32, custom firmware, Bluetooth, and AWS IoT. Smart devices, real-time sync, low-latency control. - AI/ML Integration: ChatGPT, ML models, and automation embedded into mobile/web apps. 5+ AI chatbots, 4 ML features built. - Web Backend + Frontend: Full-stack engineer using Node.js, React, Laravel, MySQL. Solid APIs, fast UIs, maintainable code. 📱 𝐑𝐞𝐜𝐞𝐧𝐭 𝐖𝐨𝐫𝐤 - BLE-based TV Lift Controller: IoT app + firmware. 99.9% uptime. Reduced support tickets by 85%. - Fitness Social Platform (Flutter): Scaled to 50K+ users. 40% MoM growth. - QSR Ops Platform: Internal tool for 200+ fast food locations (Taco Bell, KFC, etc). Saved $1.2M/yr in ops cost. - Sports Team App: Booking, scheduling, payments. Now used by 15K+ hockey players. 🧰 𝐒𝐭𝐚𝐜𝐤 Mobile: Flutter, Dart, React Native, Swift Web: React.js, Node.js, Laravel IoT: BLE, ESP32, Arduino, AWS IoT AI: Python, OpenAI API, TensorFlow DevOps: CI/CD, GitHub Actions, Docker Tools: Figma, Postman, Firebase, MySQL ✅ 𝐖𝐡𝐲 𝐌𝐞? - Built MVPs and scaled platforms — not just code, real products - Own the process — architecture to deployment - Communicate clearly - Proactive - Detail-oriented