Denys Chepiha

• Principais realizações:
• Lançou uma plataforma de serviços profissionais para desenvolvimento web - ativa, ativamente utilizada e gerando trabalho real de clientes.
• Projetou, construiu e entregou uma plataforma empresarial completa para a Martin Projektbau (empresa de construção, Suíça) - incluindo conteúdo gerado por IA, conteúdo de vídeo e todos os serviços de produção conectados.
• Desenvolvendo Chepiha Service - um aplicativo dedicado à venda e gestão de serviços de reparação de equipamentos John Deere (atualmente em desenvolvimento ativo).
• Construiu e lançou a CHEPIO.TECH como plataforma de serviços principal - ponto de partida para um ecossistema de produtos em crescimento.
• Integrou a entrega de e-mail e análises em todas as plataformas, garantindo plena prontidão operacional desde o primeiro dia.
• Cobriu todos os aspectos legais e de conformidade: termos de serviço, política de privacidade, política de cookies e requisitos do RGPD.
• Fundou a CHEPIO.TECH como empresa independente de serviços de desenvolvimento, gerenciando tanto o negócio quanto toda a entrega técnica.
• Construiu e entregou uma plataforma empresarial completa para a Martin Projektbau - uma empresa de construção que está a lançar na Suíça. A plataforma inclui conteúdo gerado e adaptado por IA, bem como conteúdo de vídeo, tudo adaptado à UI e à marca.
• Conectou todos os serviços de produção críticos - entrega de e-mail, rastreamento analítico e integrações de terceiros - garantindo que cada plataforma esteja totalmente operacional desde o primeiro dia.
• Atualmente desenvolvendo Chepiha Service - um aplicativo independente para venda e gestão de serviços de reparação de equipamentos agrícolas John Deere.
• Projetou e lançou a CHEPIO.TECH como plataforma principal para demonstrar e vender serviços de desenvolvimento, servindo como ponto de lançamento para uma suíte crescente de produtos e serviços.
• Gerenciou a entrega de projetos de clientes de ponta a ponta: descoberta, design de arquitetura, desenvolvimento, QA, implantação e entrega.
• Tratou de toda a documentação legal necessária para uma empresa de serviços profissionais, incluindo políticas de privacidade e cookies em conformidade com o RGPD.

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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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• Principais realizações:
• Construiu e lançou uma plataforma de gestão de fábrica em tempo real utilizada diariamente por equipas de produção em vários locais.
• Desenvolveu um leitor de PDF personalizado para web e mobile, suportando fluxos de trabalho documentais complexos de múltiplas páginas.
• Construiu um chat em tempo real completo com funcionalidade de mensagens completa, confirmações de leitura e atualizações ao vivo.
• Desenvolveu serviços de Drag & Drop personalizados para gestão visual de processos e personalização de fluxos de trabalho.
• Construiu tabelas de dados de alto desempenho com grandes conjuntos de dados, filtragem multicoluna, ordenação e paginação.
• Atingiu 80% de cobertura de testes unitários e de integração (Jest, React Testing Library), reduzindo regressões em módulos críticos.
• Assumiu a entrega full-stack: projetou e manteve toda a API backend (Node.js, Express) que alimenta a plataforma.
• Configurou o CI/CD no Windows Server, administrou o servidor, geriu o PM2 e manteve as atualizações de pacotes para o deployment do Next.js.
• Criou funcionalidade de mapa interativo usando Leaflet.js e Geoman para rastreamento visual em tempo real das operações da fábrica.
• Projetou um dashboard de widgets analíticos com widgets de dados configuráveis e interativos para insights operacionais.
• Aplicou estratégias de cache e otimizações de desempenho, melhorando a velocidade de processamento de dados e a capacidade de resposta do dashboard em ~35%.
• Migrou todo o frontend de plain JavaScript para strict TypeScript, reduzindo erros relacionados com tipos e melhorando a DX.
• Substituiu o Elastic UI por uma biblioteca de componentes React totalmente personalizada, reduzindo o tempo de desenvolvimento para novas funcionalidades em 25%.
• Desempenhou um papel fundamental na construção de uma plataforma de gestão de processos de fábrica e industriais do zero até ao lançamento completo em produção.
• Desenvolveu um leitor de PDF personalizado integrado tanto na web como no React Native mobile, suportando navegação de documentos complexa, paginação e fluxos de trabalho de anotação.
• Construiu um chat em tempo real completo com entrega de mensagens, confirmações de leitura, histórico e atualizações ao vivo via WebSockets.
• Desenvolveu serviços de Drag & Drop personalizados usando React DnD, permitindo às equipas gerir e personalizar visualmente os processos de produção e fluxos de trabalho.
• Construiu tabelas de dados de alto desempenho que lidam com grandes conjuntos de dados com filtragem multicoluna, ordenação, paginação e exportação - uma interface central em toda a plataforma.
• Assumiu a plena responsabilidade do backend: projetou APIs RESTful e RPC (Node.js, Express), implementou autenticação JWT, lógica de negócio e a camada de dados PostgreSQL.
• Configurou e administrou pipelines CI/CD no Windows Server: configurou e geriu PM2 para gestão de processos, tratou de atualizações de pacotes e manutenção para o ambiente de deployment do Next.js.
• Desenvolveu um mapa Leaflet.js interativo com zonas SVG personalizadas, marcadores e integração com Geoman, permitindo o rastreamento espacial das operações da fábrica.
• Projetou e entregou uma interface de widgets analíticos - os utilizadores podiam configurar, redimensionar e interagir com dashboards de dados operacionais ao vivo.
• Aplicou estratégias de cache e otimizações de desempenho no frontend e backend, melhorando os tempos de carregamento do dashboard e a velocidade de processamento de dados.
• Projetou e construiu a arquitetura geral da aplicação, escalou a plataforma conforme os requisitos cresciam e tomou decisões técnicas chave para fiabilidade e manutenibilidade.
• Escreveu testes unitários e de integração (Jest, React Testing Library) atingindo 80% de cobertura de testes.
• Estendeu a plataforma com módulos React Native para técnicos de campo, permitindo acesso móvel aos fluxos de trabalho principais.

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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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