I build, modernize and rescue production React and Next.js applications. My work includes complex TypeScript frontends, server components and APIs, authentication, billing, PostgreSQL/Supabase data flows, Cloudflare Workers, performance profiling and reliable deployment. I can take over an existing codebase, diagnose architectural and runtime problems, stabilize critical user journeys, remove duplicated logic and deliver focused tested changes. Mendelio is a production example: a multi-product Next.js 16 / React 19 platform with AI workflows, real-time voice, billing and cloud-edge infrastructure.