Denys Chepiha

• Key Achievements:
• Solo-built a complete EdTech platform from scratch - public website, student dashboard, admin panel, and structured knowledge library.
• Designed and delivered a frontend curriculum covering HTML, CSS, JavaScript, TypeScript, React, and Next.js with portfolio preparation, CV guidance, and interview coaching.
• Engineered a knowledge library with 10 topics, 87 sections, 170 code examples, and 41 interactive demos built with Monaco Editor.
• Built full student-facing infrastructure: lessons, session recordings, credits, announcements, and account management.
• Implemented complete admin tooling: user management, role-based access, bans, audit logs, and platform settings.
• Integrated Clerk authentication, Stripe payments, and LiveKit for live learning sessions.
• Solo-founded and built School CHEPIO.TECH - an online frontend school and custom EdTech platform. Own the full lifecycle from product strategy and curriculum design to platform architecture, full-stack development, and ongoing operations.
• Built the complete platform solo using Next.js 15, React 19, and TypeScript - covering public marketing site, authenticated student dashboard, structured knowledge library, and a full admin control panel.
• Designed and delivered a frontend curriculum from HTML fundamentals through Next.js, with structured modules on TypeScript, React patterns, portfolio preparation, CV guidance, and technical interview coaching.
• Engineered a knowledge library with 10 topics, 87 sections, 170 code examples, and 41 interactive in-browser demos powered by Monaco Editor.
• Built all student-facing infrastructure: lesson access, live session recordings, credit system, platform announcements, and full account management.
• Implemented admin tooling covering user management, role-based access control, ban management, credit adjustments, audit logs, and platform-wide settings.
• Integrated Clerk for authentication, Stripe for payments, and LiveKit for live learning sessions; added full i18n via next-intl and test coverage with Vitest and Playwright.

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• Key Achievements:
• Launched a professional services platform for web development - live, actively used, and generating real client work.
• Designed, built, and delivered a complete business platform for Martin Projekt Group (construction company, Switzerland) - including AI-generated content, video content, and all production services connected.
• Developing Chepiha Service - a dedicated application for selling and managing John Deere equipment repair services (currently in active development).
• Built and launched CHEPIO.TECH as the flagship services platform - the starting point for a growing ecosystem of products.
• Integrated email delivery and analytics across all platforms, ensuring full operational readiness from day one.
• Covered all legal and compliance aspects: terms of service, privacy policy, cookie policy, and GDPR requirements.
• Founded CHEPIO.TECH as an independent development services company, managing both the business and all technical delivery.
• Built and delivered a full-featured business platform for Martin Projekt Group - a construction company launching in Switzerland. The platform includes AI-generated and AI-adapted content as well as video content, all tailored to match the UI and brand.
• Connected all critical production services - email delivery, analytics tracking, and third-party integrations - ensuring each platform is fully operational from day one.
• Currently developing Chepiha Service - a standalone application for selling and managing John Deere agricultural equipment repair services.
• Designed and launched CHEPIO.TECH as the primary platform for demonstrating and selling development services, serving as the launchpad for a growing suite of products and services.
• Managed end-to-end client project delivery: discovery, architecture design, development, QA, deployment, and handoff.
• Handled all legal documentation required for a professional services business, including GDPR-compliant privacy and cookie policies.

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• Key Achievements:
• Led a gradual modernization of a large legacy frontend by introducing a "strangler" approach: new features on Next.js/Vike while safely isolating legacy modules to avoid big-bang rewrites.
• Rebuilt critical UI flows with SSR/SSG where applicable, improving perceived load time and reducing layout shifts.
• Implemented advanced code-splitting and dynamic imports for heavy widgets, significantly reducing initial bundle size.
• Introduced a component-driven architecture to unify legacy and new UI patterns across the product.
• Built an internal UI kit to replace inconsistent legacy components, increasing UI consistency and accelerating development.
• Optimized rendering performance using memoization, virtualization, and state isolation, improving responsiveness on low-end devices.
• Implemented a robust state management strategy (feature-level boundaries, selectors, derived state) to reduce re-renders and simplify complex screens.
• Established typed API layer patterns (clients, centralized errors, retries/cancellation), improving stability of data-heavy pages.
• Designed a resilient real-time update strategy (polling/websocket hybrid, backoff, throttling) to keep UI fresh without wasting resources.
• Hardened security in legacy areas (safe URL parsing, input sanitization), reducing XSS risk.
• Implemented responsive images with srcset/sizes and device-aware breakpoints to avoid over-downloading on mobile.
• Introduced modern formats (WebP/AVIF) with graceful fallbacks for legacy browsers, improving quality-to-size ratio.
• Added lazy-loading and prioritized preloading for above-the-fold assets, improving perceived performance of landing and lobby pages.
• Refactored legacy components that rendered images incorrectly (missing dimensions, layout shifts), reducing CLS across pages.
• Led a full refactoring of the sound system for an online casino platform, completely redesigning the sound loading and playback strategy to improve performance, scalability, and maintainability.
• Optimized image delivery across the application by updating core components, introducing lazy loading, and improving SVG handling.
• Upgraded the frontend architecture by fully integrating Strapi v5 with Cloudflare Images, designing and implementing the complete image delivery pipeline.
• Designed and implemented a custom Strapi v5 provider from scratch to integrate with Cloudflare Images, as no existing libraries or ready-made solutions were available.
• Developed Cloudflare Workers to serve images stored both in Cloudflare and AWS S3, ensuring flexible, scalable, and performant asset delivery.
• Implemented a cache-first strategy for image loading via Cloudflare, significantly reducing bandwidth consumption and image delivery costs.
• Actively mentored Junior and Middle Frontend Developers, supporting their growth through guidance, feedback, and best practices.
• Conducted regular code reviews to maintain high code quality, architectural consistency, and long-term maintainability.
• Designed and implemented complex, interactive user interfaces with a strong focus on performance, scalability, and user experience.
• Improved application security by implementing protection against Cross-Site Scripting (XSS) vulnerabilities caused by script injection via URL parameters.
• Modernized legacy codebases by migrating class-based React components to functional components using modern React patterns.
• Investigated and resolved long-standing legacy bugs, reducing technical debt and improving platform stability.

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• Key Achievements:
• Built and launched a real-time factory management platform used daily by production teams across multiple sites.
• Improved data processing speed and dashboard responsiveness by ~35% through backend optimization and frontend memoization strategies.
• Achieved 85% unit and integration test coverage (Jest, React Testing Library), reducing regressions in critical modules by ~40%.
• Replaced Elastic UI with a fully custom React component library, improving UI consistency and cutting dev time for new features by 25%.
• Extended platform to mobile with basic React Native modules, expanding platform access for technicians in the field.
• Migrated entire frontend from plain JavaScript to strict TypeScript, reducing type-related bugs and improving DX.
• Created interactive map functionality using Leaflet.js and Geoman, enabling real-time visual tracking of factory operations.
• Designed a modular infrastructure layer using PM2, environment-based configs, and structured logging.
• Actively contributed to CI/CD pipeline, streamlining deployment and reducing manual QA effort.
• Played a key role in building a factory and industrial process management platform from the ground up, leading it to full production release.
• Developed complex modules including real-time dashboards, custom CRM tools, and a built-in PDF reader using React, Next.js, TypeScript, Redux Toolkit, and React Hook Form.
• Migrated codebase from vanilla JavaScript to TypeScript, significantly improving scalability and maintainability.
• Engineered an interactive Leaflet.js map with custom SVG zones, markers, and Geoman integration, enabling spatial tracking of factory operations.
• Created backend services using Node.js, Express, and both REST and RPC APIs; implemented secure JWT-based authentication, structured logging, PM2 process management, and CORS handling.
• Refactored UI components, replacing Elastic UI with a custom component library tailored to client specifications.
• Wrote unit and integration tests (Jest, React Testing Library) achieving 85% test coverage.
• Ensured full-stack integration and performance optimizations, handling infrastructure-level tasks including CORS, API versioning, and deployment workflows.
• Contributed to cross-platform functionality by extending the app with React Native modules.
• Designed and owned the overall application architecture, making key technical decisions to ensure scalability, reliability, and long-term maintainability.
• Solved complex technical and product challenges, balancing performance, security, and user experience across the full stack.

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• Key Achievements:
• Delivered 3 fully customized, high-performance e-commerce storefronts under strict client deadlines.
• Reduced average page load time by 30% through SSR and component-level rendering optimizations.
• Integrated multi-payment systems, boosting flexibility for international clients.
• Led frontend mentoring for 3 junior developers, improving onboarding and code quality across the team.
• Introduced XState for UI state machines, reducing async bugs by ~50% in checkout and cart logic.
• Spearheaded the development of a scalable e-commerce platform, enabling rapid deployment of customized client storefronts based on Magento 2 and a React/Next.js frontend stack.
• Delivered three full-scale production-ready e-commerce stores, leveraging TypeScript, GraphQL, and component-driven architecture to ensure performance, reusability, and scalability.
• Integrated advanced features including multi-payment gateway support, smart product search, custom auth flows, and real-time analytics tools.
• Collaborated closely with backend engineers to maintain seamless API integration and stable cross-system performance.
• Took ownership of core platform improvements: optimized rendering logic, modularized the codebase, and introduced XState for managing complex state machines.
• Acted as a technical mentor to junior developers, providing guidance on architecture, best practices, and conducting regular code reviews to maintain high code quality across projects.
• Contributed to design system evolution and internal documentation, improving onboarding and cross-team collaboration.

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• Key Achievements:
• Migrated the core platform from Backbone to React + Redux-Saga, cutting average page-load time by 35% and simplifying future enhancements.
• Implemented a custom SSR pipeline with Next.js, boosting SEO visibility and lifting organic traffic by 20%.
• Refactored and standardized a large legacy codebase, reducing future development effort by ≈25% and eliminating 12k+ lines of dead code.
• Designed and delivered 15+ animated marketing landing pages, increasing campaign conversion rates by 22% and extending average session duration by 18%.
• Mentored three junior developers through pair-programming and code reviews, raising overall test coverage from 30% to 65% and accelerating their ramp-up to full productivity.
• Contributed to the development of a feature-rich online education platform used by thousands of learners to improve their English through interactive lessons, live classes, and gamified exercises.
• Built and optimized complex UI components using React, Redux-Saga, and GraphQL, supporting asynchronous data flows and personalized learning paths.
• Developed responsive, animated landing pages for marketing campaigns, balancing creative UX design with high-performance rendering and SEO optimization.
• Refactored and updated legacy codebases to enhance stability, readability, and long-term maintainability across both core and promotional products.
• Participated in code reviews and mentored junior developers, helping the team adopt modern best practices and improve code quality.
• Contributed to both feature development in the main learning system and UX-heavy marketing initiatives, acting as a bridge between product and engineering.

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• Key Achievements:
• Migrated the core platform from jQuery to React, improving performance and maintainability.
• Built a custom SSR system that improved SEO visibility and increased organic traffic by 20%.
• Refactored and standardized legacy codebase, cutting future dev time by ~25%.
• Contributed to Prozorro - a national public procurement system - ensuring UI consistency under high user load.
• Mentored junior team members during the migration, introducing React best practices and code reviews.
• Developed and maintained several client-facing React-based web applications, focusing on responsive layout, cross-browser compatibility, and performance optimization.
• Implemented Next.js with Server-Side Rendering (SSR) to improve SEO and initial load time across international web projects.
• Migrated and modernized legacy jQuery codebases, ensuring consistent behavior and styling across major browsers while introducing modular React components.
• Configured and maintained frontend build processes using Gulp, enabling faster development cycles and custom deployment pipelines.
• Participated in third-party platform integrations, including contributions to Prozorro - a national public procurement system - ensuring UI consistency and stability under high user load.
• Assisted in QA/debugging on external projects, identifying and resolving cross-platform bugs within strict deadlines.

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• Key Achievements:
• Delivered a complete fullstack booking platform independently, from backend to production deployment.
• Developed modular, reusable frontend components, improving UX and code reusability.
• Implemented secure authentication and robust form validation using Django and MySQL.
• Designed and built a full-cycle booking system for a beauty salon, enabling customers to browse services, register, and schedule appointments online.
• Developed the backend using Python (Django) and MySQL, implementing business logic, models, and secure user authentication.
• Created a responsive and user-friendly frontend with HTML, CSS, and vanilla JavaScript, ensuring compatibility across devices and browsers.
• Deployed the project end-to-end to a live production environment, handling server setup, deployment, and testing workflows.
• Delivered a fully functional, production-ready product independently, showcasing strong fullstack ownership and end-to-end development skills.

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• Key Achievements:
• Developed 10+ landing pages optimized for mobile and cross-browser performance.
• Learned and applied foundational frontend techniques while delivering production-quality layouts.
• Improved asset delivery by compressing and optimizing images and fonts, enhancing UX.
• Built interactive components using vanilla JavaScript, gaining hands-on experience in real projects.
• Developed responsive landing pages using HTML5 and CSS3, with a strong focus on mobile-first design and performance optimization.
• Compressed and optimized static assets (images, fonts) to improve page load speed, contributing to faster UX and better SEO scores.
• Ensured full cross-browser compatibility and maintained clean, modular code following early best practices.
• Learned and applied foundational JavaScript to add interactivity and support dynamic behavior on promotional pages.
• Collaborated with designers and more senior developers, gaining practical experience in real-world project workflows.
• Actively studied frontend development technologies and web standards, laying the groundwork for future fullstack proficiency.

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