Serhii R.

Senior Full-Stack Developer | React, Node.js, TypeScript | SaaS

Hi, I'm Serhii – a senior full-stack developer with 15 years building production web applications for founders and long-running product teams. On Upwork I've delivered 12,000+ hours at a 100% Job Success score and $400K+ earned, including a 4+ year React and Node.js engagement where I worked across the full stack for one client – 7,700+ hours on a single partnership. That's the kind of work I aim for: staying with a product long enough to make it good. My recent work spans long-running SaaS platforms, workforce-management systems, data-heavy dashboards, React Native mobile apps in production, and full-stack rewrites of legacy systems. What I do: • Full-stack web apps – React, Vue.js, and TypeScript on the front end; Node.js, Express, NestJS, and PHP/Laravel on the back end. • SaaS platforms & MVPs – auth, dashboards, billing, multi-tenant architecture, from first commit to paying customers. • React Native mobile – cross-platform apps from a shared codebase, shipped to the App Store and Google Play. • APIs & integrations – REST and GraphQL APIs, third-party integrations, and backend services built to stay fast under real load. • Data-heavy features – analytics, reporting, and processing of large data volumes with PostgreSQL, MySQL, and MongoDB; complex queries and schema design I actually enjoy. • Real-time features – WebSockets, live updates, chat, and collaborative flows. • DevOps & cloud – AWS (EC2, S3, Lambda, DynamoDB, SES, Route 53), CI/CD, and cloud deployment so what I build ships reliably. • Rescue & refactor – joining stalled or messy projects, stabilising them, and moving them forward without a rewrite where possible. How I work: I start from the outcome you actually need, not just the ticket. You get clear communication, honest estimates, weekly progress you can see, and clean, maintainable code that lives in your repository from day one – no lock-in. I'm equally comfortable owning a greenfield build, joining an existing team, or rescuing a stalled project and getting it back on track. I think about security, edge cases, and performance before they become problems. A strong fit for: • SaaS platforms, dashboards, and internal tools • React Native mobile apps (new builds or long-term maintenance) • Custom web applications from idea to launch • API and backend development on Node.js, NestJS, or Laravel • Performance, scaling, and refactoring of existing apps • Long-term partnerships where the same developer stays with the product Tech I use daily: JavaScript, TypeScript, React, React Native, Vue.js, Node.js, Express, NestJS, PHP, Laravel, GraphQL, REST APIs, WebSockets, PostgreSQL, MySQL, MongoDB, Redis, AWS (EC2, S3, Lambda, DynamoDB), Docker, and Git. Why clients keep coming back: a 100% Job Success record over 15 years, and long-running engagements where the same client returns for the next phase – one of them lasted 4+ years. I treat your product like my own: reliable, communicative, and genuinely invested in it working in production. If you need a senior developer who can take a product from idea to launch and keep improving it for years, send me a message with a few details about what you're building. I'll reply with honest thoughts on scope, approach, and timeline. Let's talk.