Anton M.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 7, 2026.

Senior full-stack engineer (Next.js, TypeScript, Supabase) who stays: my two longest Upwork engagements ran 2,400+ and 1,900+ hours, each over $100K. I join product teams for the long run, and I take apps built in Lovable, Replit or Claude Code to secure, tested production. "I've been a developer myself for 20+ years, led large teams, and founded a couple companies... I've only came across a few exceptional developers such as Anton." - client review 10+ years of experience, 7,400+ hours on Upwork, Top Rated Plus, 100% Job Success. In product teams, I own features end to end in existing React and Next.js codebases: architecture, implementation, tests and release. Most of my Upwork hours come from engagements like this, where I stayed for years, not weeks. I worked on internal operations tools at Robinhood, where correctness, permissions and audit trails mattered more than speed. For founders, the work usually starts with an app that works in a demo but isn't safe to launch. What I usually find and fix: - Supabase row-level security that is off or too open, so one user can see another user's data - Secret keys exposed in the browser or committed to the repo - Payments and webhooks that can charge twice or fall out of sync - Sign-up, login and password reset flows that break for real users - No tests, no staging, and everything running on the founder's personal accounts I keep what works and fix the rest, without rewriting everything. You get a clear report in plain English, then fixes in small, reviewed steps. What clients hire me for: - Long-term senior engineer in a product team (part-time or full-time) - Security and code reviews of AI-built apps (Lovable, Replit, Claude Code, Cursor) - Taking over an existing codebase and shipping it to production - Supabase and PostgreSQL: schema design, row-level security, multi-tenant setups, performance - Payments: subscriptions, checkout and webhooks that reconcile exactly - Moving apps to your own GitHub, Supabase and Vercel accounts - AI features with the OpenAI and Claude APIs, with costs and failures handled Selected work (see Portfolio): - The Earth Prize: led development of a global competition platform for students (Next.js, Supabase, Okta SSO, admin panel) - Business compliance platform: member portal, recurring billing and HubSpot CRM integration - Switzerland's largest B2B vehicle marketplace: client app and back office - GlassFlow: high-performance UI for real-time data workflows How I work: I use Claude Code every day, but I read every diff myself. Anything touching payments, permissions or user data is reviewed by hand and covered by tests. I write short, clear updates and I'm in CET, with overlap to US mornings. Stack: Next.js, React, TypeScript, Node.js, Supabase, PostgreSQL, Stripe, Tailwind, Vercel, Playwright, OpenAI and Claude APIs. Send me a link to your app or describe the problem. Within 24 hours you'll get how I'd approach it, a rough timeline, and an honest answer on whether I'm the right fit.