Denis Z.

Startups hire me when they need more than a coder — they need someone who takes ownership of architecture and ship I’m a Full Stack Developer with 7+ years of experience building scalable, secure, and high-performance applications. I specialize in Next.js (React.js) frontend development and Node.js (Express.js / Express JS, NestJS) backend engineering, delivering end-to-end solutions for startups and enterprises. 🔹 Front end expertise: 7+ years of experience as a Frontend Developer / Frontend React Developer / Frontend Developer React, building modern web apps with React.js, React JS, ReactJS, React Web Developer experience, Full Stack React Developer and Full Stack React JS expertise. Skilled in frontend design, frontend react, frontend designer, frontend engineer, responsive design, accessibility (WCAG), React Native Developer for cross-platform apps, and advanced UI development with Next.js, React Next JS, React JS Website Development, Tailwind CSS, Material UI, Redux, Context API. 🔹 Back end expertise: 5+ years of experience in backend engineering with Node.js, Express.js, Express JS, and NestJS. Building secure, scalable systems with REST API, GraphQL, WebSockets, authentication (JWT, OAuth, social logins), and payment integrations (Stripe, PayPal, LiqPay, WayForPay, Fondy). Strong in database design using PostgreSQL, MySQL, MongoDB, plus Prisma ORM, Sequelize, Mongoose. Experienced in React.js Node.js full stack solutions and React JS Node JS architectures. 🔹 DevOps & Deployment: Docker, GitHub Actions, CI/CD pipelines, AWS, Vercel, DigitalOcean, Heroku. Expert in cloud hosting, scalable infrastructures, performance monitoring, and database optimization. 🔹 Domains: E-commerce and Marketplace Development (multi-vendor, auctions, bidding, barter systems) SaaS platforms with subscription and secure payment systems CRM systems, Admin dashboards, Analytics platforms, Booking solutions Real-time Applications (chat apps, notifications, WebSocket integrations) AI-powered applications (search, recommendation systems, image recognition) Migration of legacy apps to modern React.js + Node.js (React JS Node JS) full stack solutions Experience with international collaboration including React Developers Ethiopia ✅ What I can deliver for you: Scalable SaaS platforms with subscription systems & secure gateways E-commerce & Marketplace apps (multi-vendor, auctions, bidding, barter systems) Admin dashboards, analytics systems, CRM, user & role management Real-time applications (chat apps, notifications, WebSocket integrations) SEO-friendly, fast, and responsive web apps (SSR/SSG, React JS Website, React Next JS apps) Migration of legacy codebases to modern stacks (React.js, Next.js, Node.js, Express.js, Express JS) AI & API integrations (ChatGPT, OpenAI API, image recognition, recommendation engines) Full-cycle product development (from MVP to production launch) 🔑 Keywords for SEO & Upwork Search: Frontend Developer, Frontend React, Frontend Designer, Frontend Design, Frontend Engineer, Frontend Developer React, Frontend React Developer, Frontend React, Front End Developer React, React Developer, React Native, React Native Developer, React JS, React JS Developer, React.js Developer, ReactJS Developer, React Developers Ethiopia, React Web Developer, Full Stack React Developer, Full Stack React JS, React Next.js, React JS Website, React.js Website Development, Java React, UI Developer, UX Developer, Responsive Web Design, SPA Developer, PWA Developer, React Hooks, Redux, Context API, Server-Side Rendering, Static Site Generation, Tailwind CSS, Material UI, HTML5, CSS3, JavaScript ES6+, API Developer, API Integration, WebSocket Developer, Chat App Developer, Real-Time Applications, Multi-language Support, Multi-currency Support, SEO Optimization, Web Performance Optimization, Code Review, Unit Testing, Integration Testing, End-to-End Testing, Jest, Cypress, Agile Development, Scrum, Kanban, Git, GitHub, GitLab, CI/CD, Mobile-First Design, Cross-Browser Compatibility, Accessibility Standards, WCAG, Debugging, Performance Profiling, API Documentation, Swagger, Postman, Third-Party API Integration, SaaS Development, Startup Development, MVP Development, Product Launch, Scalability Planning, Code Refactoring, Legacy Code Migration, Version Control, Open Source Contribution, Collaboration Tools, Trello, Jira, Asana, Time Management, Remote Teamwork, Communication Skills, Problem Solving, Critical Thinking, Continuous Learning, Mentoring, Technical Leadership, Project Management, End-to-End Web Solutions, Web Design Integration, Bonus System, Referral System, Trust Rating System, Node.js, Express.js, Node js, Express js, PostgreSQL, Mongoose, Stripe, PayPal, REST API, GraphQL, JWT, OAuth, Authentication, Authorization, Payment Integration, LiqPay, WayForPay, Fondy, Secure Transactions, CRUD Operations, Marketplace Development, E-commerce, Auction Platform, Real-Time Apps, WebSocket, AI Integration, AWS