YoN (yes-or-no) startup — a platform for predictions on sports, politics and culture: users bet on a yes/no outcome using an internal virtual currency. Fullstack development (React / NestJS).

Achievements:
* Co-launched the MVP in 2 months, which helped attract the next investment round. I built the entire frontend alone; on the backend I worked in pair with a lead developer — took over authorization, admin panel, reward economy, referrals, leaderboards and queues, freeing my partner to focus on the core market engine (pricing, matching, settlement)
* Frontend: built the React+TS app from scratch, mobile-first. Custom design system based on MUI per Figma layouts; infinite scroll on @tanstack/react-query + @tanstack/react-virtual; live prices via SSE with auto-reconnect and backoff; optimistic updates on buy/sell of shares
* Full test suite: unit (Vitest), integration (RTL), E2E (Playwright); CI/CD with auto-deploy to VPS

Year: 2025

Customer: InstaDev agency