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Hi, I’m Kostiantyn Stadnychuk, a Full Stack Engineer with 8+ years of experience designing and building scalable, high-performance web and eCommerce applications. I specialize in React, Next.js, Node.js, and Shopify, with a strong focus on API design, performance optimization, and cloud infrastructure (AWS, Firebase). I enjoy turning complex requirements into robust, maintainable software and leading teams in Agile environments. I’m passionate about clean architecture, headless commerce, and AI-assisted development that drives efficiency and innovation. I thrive on delivering feature-rich user experiences, improving CI/CD automation, and mentoring colleagues to raise code quality and productivity.…Hi, I’m Kostiantyn Stadnychuk, a Full Stack Engineer with 8+ years of experience designing and building scalable, high-performance web and eCommerce applications. I specialize in React, Next.js, Node.js, and Shopify, with a strong focus on API design, performance optimization, and cloud infrastructure (AWS, Firebase). I enjoy turning complex requirements into robust, maintainable software and leading teams in Agile environments. I’m passionate about clean architecture, headless commerce, and AI-assisted development that drives efficiency and innovation. I thrive on delivering feature-rich user experiences, improving CI/CD automation, and mentoring colleagues to raise code quality and productivity.

Kostiantyn Stadnychuk

Full Stack Developer, Front-End Developer, Back-End Developer, +2

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Hi, I’m Kostiantyn Stadnychuk, a Full Stack Engineer with 8+ years of experience designing and building scalable, high-performance web and eCommerce applications. I specialize in React, Next.js, Node.js, and Shopify, with a strong focus on API design, performance optimization, and cloud infrastructure (AWS, Firebase). I enjoy turning complex requirements into robust, maintainable software and leading teams in Agile environments. I’m passionate about clean architecture, headless commerce, and AI-assisted development that drives efficiency and innovation. I thrive on delivering feature-rich user experiences, improving CI/CD automation, and mentoring colleagues to raise code quality and productivity.…Hi, I’m Kostiantyn Stadnychuk, a Full Stack Engineer with 8+ years of experience designing and building scalable, high-performance web and eCommerce applications. I specialize in React, Next.js, Node.js, and Shopify, with a strong focus on API design, performance optimization, and cloud infrastructure (AWS, Firebase). I enjoy turning complex requirements into robust, maintainable software and leading teams in Agile environments. I’m passionate about clean architecture, headless commerce, and AI-assisted development that drives efficiency and innovation. I thrive on delivering feature-rich user experiences, improving CI/CD automation, and mentoring colleagues to raise code quality and productivity.

Available to hire

Hi, I’m Kostiantyn Stadnychuk, a Full Stack Engineer with 8+ years of experience designing and building scalable, high-performance web and eCommerce applications. I specialize in React, Next.js, Node.js, and Shopify, with a strong focus on API design, performance optimization, and cloud infrastructure (AWS, Firebase). I enjoy turning complex requirements into robust, maintainable software and leading teams in Agile environments.

I’m passionate about clean architecture, headless commerce, and AI-assisted development that drives efficiency and innovation. I thrive on delivering feature-rich user experiences, improving CI/CD automation, and mentoring colleagues to raise code quality and productivity.

Skills

Experience Level

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Work Experience

Senior Frontend Developer at Terrasparq Tech Pvt Ltd

August 1, 2025 - October 20, 2025

Developed responsive, high-performance user interfaces from Figma designs using React, Next.js, and Tailwind CSS. Optimized serverless backend services with Firebase and Node.js to enhance reliability and scalability. Integrated third-party APIs such as Stripe and Contentful for secure payments and dynamic content delivery. Applied lazy loading, code splitting, and memoization to improve Core Web Vitals. Implemented CI/CD pipelines (GitHub Actions) and improved unit/integration test coverage for consistent code quality.

Senior Shopify Developer at MGROUP Shopify Agency

October 1, 2024 - October 20, 2025

Designed and built custom Shopify themes and apps using Liquid, React, and Shopify Polaris. Integrated Klaviyo, Recharge, and Yotpo to improve retention and conversion rates. Created Shopify apps with Node.js and Express to automate backend workflows and extend store features. Developed headless Shopify architecture with Next.js and Storefront API, reducing page load times by 40%. Boosted store performance metrics by 35% through image optimization, Liquid refactoring, and caching strategies.

Full Stack Engineer at Apple (Contract)

October 1, 2024 - October 20, 2025

Led full-stack development of internal tools and LLM-assisted agents improving developer productivity. Designed and deployed RESTful and GraphQL APIs with automated testing to ensure reliability. Spearheaded cross-team code reviews and debugging initiatives to improve software quality. Evaluated LLM-generated code for performance, maintainability, and correctness. Collaborated on prompt engineering and AI integration strategies to refine model consistency.

Full Stack Developer at GlobalLogic

May 1, 2022 - October 20, 2025

Delivered scalable web solutions across AWS, Azure, and GCP environments. Architected and maintained microservices using Node.js, Express, and Docker. Managed Agile sprint planning and mentored junior developers to ensure timely, high-quality releases. Leveraged big data and AI-powered analytics tools to support enterprise projects.

Frontend Developer at Innosoft-Group

March 1, 2020 - October 20, 2025

Migrated legacy systems from jQuery to React and Redux, improving UX for 10,000+ users. Enhanced CI/CD reliability by implementing Jest and Enzyme testing with 75% coverage. Built high-performance Next.js web apps that boosted SEO and organic traffic. Modernized codebase using React Hooks and functional components for cleaner, reusable logic.