Andrii K.Private profile: Upwork shows its earnings only to signed-in members, so we check it every few weeks, not daily. MRR here is a rough estimate (Upwork's six-month earnings ÷ months active). Last read Nov 5, 2026.

Senior frontend developer with 5+ years of commercial experience. Specializing in real-time collaborative systems, WebSockets, complex interactive UI, and large legacy codebases. What I do best: Real-time and collaborative features. Built end-to-end real-time chat on WebSockets at a Swiss e-commerce company (15-engineer team, solo ownership of the feature). Architected the core synchronization layer for virtual classrooms in an EdTech platform: real-time teacher-student interaction, ~15 interactive exercise types, Miro-like collaborative whiteboard. Complex interactive UI. Built a Blockly-based visual formula constructor that enabled non-technical staff to configure business logic without engineers. Comfortable with drag-and-drop interfaces, animation-rich UIs, and non-trivial state management. Performance and stability. Strong with Lighthouse, Web Vitals, and Core Web Vitals optimization. Experienced in investigating and fixing production bugs in large legacy codebases using Sentry. Cover critical logic with Jest and React Testing Library. Stack: TypeScript, React (Hooks, Context API), NextJS, Gatsby, Redux Toolkit, RTK Query, WebSocket (Socket IO), Tailwind CSS, Styled Components, SCSS, Jest, React Testing Library, GraphQL, Apollo, Strapi, Sentry, GitHub Actions, GitLab CI. Best fit for projects involving: - Real-time features (chat, collaboration, live updates, sync) - Performance-critical web apps - Complex interactive interfaces (editors, builders, dashboards) - Rescue work on legacy frontend codebases - Migration to modern React, TypeScript, or NextJS How I work: communication-first. I keep clients updated proactively, ask the right questions before writing code, and stay reachable during agreed working hours. Available for part-time contracts and project-based work.