Denys Chepiha

• Kľúčové úspechy:
• Spustil platformu profesionálnych služieb pre webový vývoj - živú, aktívne využívanú a generujúcu skutočné klientske zákazky.
• Navrhol, vybudoval a dodal kompletnú obchodnú platformu pre Martin Projektbau (stavebná spoločnosť, Švajčiarsko) - vrátane obsahu generovaného AI, video obsahu a všetkých pripojených produkčných služieb.
• Vyvíja Chepiha Service - vyhradenú aplikáciu pre predaj a správu služieb opravy zariadení John Deere (aktuálne v aktívnom vývoji).
• Vybudoval a spustil CHEPIO.TECH ako vlajkovú servisnú platformu - východiskový bod pre rastúci ekosystém produktov.
• Integroval doručovanie e-mailov a analytiku na všetkých platformách, čím zabezpečil plnú prevádzkovú pripravenosť od prvého dňa.
• Pokryl všetky právne a compliance aspekty: podmienky služby, zásady ochrany súkromia, zásady súborov cookie a požiadavky GDPR.
• Založil CHEPIO.TECH ako nezávislú spoločnosť poskytujúcu vývojové služby, pričom spravuje ako podnikanie, tak aj všetky technické dodávky.
• Vybudoval a dodal kompletnú obchodnú platformu pre Martin Projektbau - stavebnú spoločnosť, ktorá sa spúšťa vo Švajčiarsku. Platforma zahŕňa obsah generovaný a adaptovaný AI a tiež video obsah, všetko prispôsobené UI a značke.
• Pripojil všetky kritické produkčné služby - doručovanie e-mailov, sledovanie analytiky a integrácie tretích strán - čím zabezpečil, že každá platforma je plne funkčná od prvého dňa.
• Aktuálne vyvíja Chepiha Service - samostatnú aplikáciu pre predaj a správu služieb opravy poľnohospodárskych strojov John Deere.
• Navrhol a spustil CHEPIO.TECH ako primárnu platformu na demonštráciu a predaj vývojových služieb, slúžiacu ako odpaľovacia rampa pre rastúcu sadu produktov a služieb.
• Spravoval dodávku klientskych projektov od začiatku do konca: discovery, návrh architektúry, vývoj, QA, nasadenie a odovzdanie.
• Spracoval všetku právnu dokumentáciu požadovanú pre spoločnosť poskytujúcu profesionálne služby, vrátane zásad ochrany súkromia a súborov cookie v súlade s GDPR.

Kliknite pre preskúmanie technológie

• 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.

Kliknite pre preskúmanie technológie

• Kľúčové úspechy:
• Vybudoval a spustil platformu na správu továrne v reálnom čase používanú denne výrobnými tímami na viacerých miestach.
• Vyvinul vlastnú čítačku PDF pre web a mobilné zariadenia, podporujúcu komplexné viacstranové pracovné postupy s dokumentmi.
• Vybudoval plne funkčný chat v reálnom čase s kompletnou funkcionalitou zasielania správ, potvrdeniami prečítania a živými aktualizáciami.
• Vyvinul vlastné služby Drag & Drop pre vizuálne riadenie procesov a prispôsobenie pracovných postupov.
• Vybudoval vysoko výkonné dátové tabuľky s veľkými dátovými sadami, viacstĺpcovým filtrovaním, radením a stránkovaním.
• Dosiahol 80% pokrytie jednotkovými testami a integračnými testami (Jest, React Testing Library), čím znížil regresie v kritických moduloch.
• Prevzal full-stack dodávku: navrhol a udržiaval celé backendové API (Node.js, Express) poháňajúce platformu.
• Nastavil CI/CD na Windows Server, spravoval server, spravoval PM2 a udržiaval aktualizácie balíčkov pre nasadenie Next.js.
• Vytvoril interaktívnu funkcionalitu mapy pomocou Leaflet.js a Geoman pre vizuálne sledovanie továrňových operácií v reálnom čase.
• Navrhol ovládací panel analytických widgetov s konfigurovateľnými, interaktívnymi dátovými widgetmi pre prevádzkové prehľady.
• Uplatnil stratégie ukladania do vyrovnávacej pamäte a optimalizácie výkonu, čím zlepšil rýchlosť spracovania dát a odozvu ovládacieho panela o ~35%.
• Migroval celý frontend z plain JavaScript na strict TypeScript, čím znížil chyby súvisiace s typmi a zlepšil DX.
• Nahradil Elastic UI plne vlastnou knižnicou komponentov React, čím skrátil čas vývoja nových funkcií o 25%.
• Zohral kľúčovú úlohu pri budovaní platformy na správu továrňových a priemyselných procesov od základov po plné produkčné vydanie.
• Vyvinul vlastnú čítačku PDF integrovanú do webu aj React Native mobile, podporujúcu komplexnú navigáciu v dokumentoch, stránkovanie a pracovné postupy anotácií.
• Vybudoval plne funkčný chat v reálnom čase s doručovaním správ, potvrdeniami prečítania, históriou a živými aktualizáciami cez WebSockets.
• Vyvinul vlastné služby Drag & Drop pomocou React DnD, umožňujúce tímom vizuálne spravovať a prispôsobovať výrobné procesy a pracovné postupy.
• Vybudoval vysoko výkonné dátové tabuľky spracovávajúce veľké dátové sady s viacstĺpcovým filtrovaním, radením, stránkovaním a exportom - centrálne rozhranie na celej platforme.
• Prevzal plnú zodpovednosť za backend: navrhol RESTful a RPC API (Node.js, Express), implementoval JWT autentifikáciu, obchodnú logiku a dátovú vrstvu PostgreSQL.
• Nakonfiguroval a spravoval CI/CD potrubia na Windows Server: nastavil a spravoval PM2 pre správu procesov, riešil aktualizácie balíčkov a údržbu prostredia pre nasadenie Next.js.
• Vyvinul interaktívnu mapu Leaflet.js s vlastnými SVG zónami, značkami a integráciou Geoman, umožňujúcou priestorové sledovanie továrňových operácií.
• Navrhol a dodal rozhranie analytických widgetov - používatelia mohli konfigurovať, meniť veľkosť a interagovať s živými ovládacími panelmi prevádzkových dát.
• Uplatnil stratégie ukladania do vyrovnávacej pamäte a optimalizácie výkonu na frontende aj backende, čím zlepšil časy načítania ovládacieho panela a rýchlosť spracovania dát.
• Navrhol a vybudoval celkovú architektúru aplikácie, škáloval platformu s rastúcimi požiadavkami a prijímal kľúčové technické rozhodnutia pre spoľahlivosť a udržovateľnosť.
• Písal jednotkové testy a integračné testy (Jest, React Testing Library) a dosiahol 80% pokrytie testami.
• Rozšíril platformu o moduly React Native pre terénnych technikov, čím umožnil mobilný prístup k hlavným pracovným postupom.

Kliknite pre preskúmanie technológie

• 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.

Kliknite pre preskúmanie technológie

• 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.

Kliknite pre preskúmanie technológie

• 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.

Kliknite pre preskúmanie technológie

• 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.

Kliknite pre preskúmanie technológie

• 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.

Kliknite pre preskúmanie technológie