Denys Chepiha

• Ključna postignuća:
• Samostalno izgradio kompletnu EdTech platformu od nule: javnu web stranicu, studentski dashboard, admin panel i strukturiranu bazu znanja.
• Osmislio i vodio frontend kurikulum koji pokriva HTML, CSS, JavaScript, TypeScript, React i Next.js, kao i pripremu portfolija, CV-ja i tehničkih intervjua.
• Razvio bazu znanja s 10 tema, 87 sekcija, 170 primjera koda i 41 interaktivnim demoom na Monaco Editoru.
• Izgradio kompletnu infrastrukturu za studente: lekcije, snimke sesija, kredite, obavijesti i upravljanje računom.
• Implementirao potpuni admin alatset: upravljanje korisnicima, pristup temeljen na ulogama, zabrane, audit logove i postavke platforme.
• Integrirao Clerk za autentikaciju, Stripe za plaćanja i LiveKit za live edukacijske sesije.
• Samostalno osnovao i izgradio School CHEPIO.TECH - online školu frontenda i prilagođenu EdTech platformu. Preuzima puni lifecycle, od produktne strategije i dizajna kurikuluma do arhitekture platforme, full-stack razvoja i svakodnevnih operacija.
• Cijelu platformu izgradio je sam koristeći Next.js 15, React 19 i TypeScript - javnu marketinšku stranicu, autentificirani studentski dashboard, strukturiranu bazu znanja i puni admin panel.
• Osmislio i vodio frontend kurikulum od osnova HTML-a do Next.js-a, sa strukturiranim modulima o TypeScriptu, React obrascima, pripremi portfolija, CV-ja i tehničkih intervjua.
• Razvio bazu znanja s 10 tema, 87 sekcija, 170 primjera koda i 41 interaktivnim demo prikazom u pregledniku na Monaco Editoru.
• Izgradio kompletnu studentsku infrastrukturu: pristup lekcijama, snimke live sesija, sustav kredita, obavijesti platforme i potpuno upravljanje računom.
• Implementirao admin alate za upravljanje korisnicima, kontrolu pristupa po ulogama, zabrane, korekcije kredita, audit logove i globalne postavke platforme.
• Integrirao Clerk za autentikaciju, Stripe za plaćanja i LiveKit za live edukacijske sesije; dodao i punu i18n podršku putem next-intl te testnu pokrivenost uz Vitest i Playwright.

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• Ključna postignuća:
• Pokrenuo platformu profesionalnih usluga za web razvoj - aktivnu, aktivno korištenu i koja generira pravi posao s klijentima.
• Dizajnirao, izgradio i isporučio kompletnu poslovnu platformu za Martin Projekt Group (građevinska tvrtka, Švicarska) - uključujući sadržaj generiran AI-jem, video sadržaj i sve povezane produkcijske usluge.
• Razvija Chepiha Service - namjensku aplikaciju za prodaju i upravljanje uslugama popravka opreme John Deere (trenutno u aktivnom razvoju).
• Izgradio i pokrenuo CHEPIO.TECH kao vodeću uslužnu platformu - polazna točka za rastući ekosustav proizvoda.
• Integrirao isporuku e-pošte i analitiku na svim platformama, osiguravajući punu operativnu spremnost od prvog dana.
• Pokrio sve pravne i aspekte usklađenosti: uvjete usluge, politiku privatnosti, politiku kolačića i zahtjeve GDPR-a.
• Osnovao CHEPIO.TECH kao neovisnu tvrtku za razvojne usluge, upravljajući i poslovanjem i svim tehničkim isporukama.
• Izgradio i isporučio kompletnu poslovnu platformu za Martin Projekt Group - građevinsku tvrtku koja se lansira u Švicarskoj. Platforma uključuje sadržaj generiran i prilagođen AI-jem te video sadržaj, sve prilagođeno UI-u i brendu.
• Povezao sve kritične produkcijske usluge - isporuku e-pošte, praćenje analitike i integracije trećih strana - osiguravajući da je svaka platforma potpuno operativna od prvog dana.
• Trenutno razvija Chepiha Service - samostalnu aplikaciju za prodaju i upravljanje uslugama popravka poljoprivredne opreme John Deere.
• Dizajnirao i pokrenuo CHEPIO.TECH kao primarnu platformu za demonstriranje i prodaju razvojnih usluga, služeći kao lansirna rampa za rastuću grupu proizvoda i usluga.
• Upravljao isporukom klijentskih projekata od početka do kraja: otkrivanje, dizajn arhitekture, razvoj, QA, implementacija i predaja.
• Riješio svu pravnu dokumentaciju potrebnu za tvrtku profesionalnih usluga, uključujući politike privatnosti i kolačića sukladne GDPR-u.

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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.

Kliknite za istraživanje tehnologije

• Ključna postignuća:
• Izgradio i pokrenuo platformu za upravljanje tvornicom u stvarnom vremenu koju dnevno koriste proizvodni timovi na više lokacija.
• Razvio prilagođeni PDF čitač za web i mobilne uređaje koji podržava složene višestraničarke tijekove rada s dokumentima.
• Izgradio potpuno funkcionalan chat u stvarnom vremenu s kompletnom funkcionalnosti razmjene poruka, potvrđivanjima čitanja i ažuriranjima uživo.
• Razvio prilagođene Drag & Drop usluge za vizualno upravljanje procesima i prilagodbu tijekova rada.
• Izgradio visokoučinkovite tablice podataka s velikim skupovima podataka, višestrukim filtriranjem po stupcima, sortiranjem i straničenjem.
• Postigao 80% pokrivenosti jediničnim testovima i integracijskih testovima (Jest, React Testing Library), smanjujući regresije u kritičnim modulima.
• Preuzeo full-stack isporuku: dizajnirao i održavao cjelokupni backend API (Node.js, Express) koji pokreće platformu.
• Postavio CI/CD na Windows Server, administrirao server, upravljao PM2 i održavao ažuriranja paketa za implementaciju Next.js.
• Stvorio interaktivnu funkcionalnost karte pomoću Leaflet.js i Geoman za vizualno praćenje tvorničkih operacija u stvarnom vremenu.
• Dizajnirao nadzornu ploču analitičkih widgeta s konfigurabilnim, interaktivnim widgetima podataka za operativne uvide.
• Primijenio strategije predmemoriranja i optimizacije performansi, poboljšavajući brzinu obrade podataka i odziv nadzorne ploče za ~35%.
• Migrirao cijeli frontend s plain JavaScript na strict TypeScript, smanjujući greške vezane uz tipove i poboljšavajući DX.
• Zamijenio Elastic UI potpuno prilagođenom bibliotekom React komponenti, smanjujući vrijeme razvoja za nove značajke za 25%.
• Igrao ključnu ulogu u izgradnji platforme za upravljanje tvorničkim i industrijskim procesima od nule do punog produkcijskog izdanja.
• Razvio prilagođeni PDF čitač integriran u web i React Native mobile, podržavajući složenu navigaciju dokumentima, straničenje i tijekove rada anotacija.
• Izgradio potpuno funkcionalan chat u stvarnom vremenu s dostavom poruka, potvrđivanjima čitanja, poviješću i ažuriranjima uživo putem WebSockets.
• Razvio prilagođene Drag & Drop usluge pomoću React DnD, omogućujući timovima vizualno upravljanje i prilagodbu proizvodnih procesa i tijekova rada.
• Izgradio visokoučinkovite tablice podataka koje obrađuju velike skupove podataka s višestrukim filtriranjem po stupcima, sortiranjem, straničenjem i izvozom - središnje sučelje na cijeloj platformi.
• Preuzeo punu odgovornost za backend: dizajnirao RESTful i RPC API-je (Node.js, Express), implementirao JWT autentifikaciju, poslovnu logiku i podatkovni sloj PostgreSQL.
• Konfigurirao i administrirao CI/CD cjevovode na Windows Server: postavio i upravljao PM2 za upravljanje procesima, rješavao ažuriranja paketa i održavanje za okruženje implementacije Next.js.
• Razvio interaktivnu kartu Leaflet.js s prilagođenim SVG zonama, markerima i Geoman integracijom, omogućujući prostorno praćenje tvorničkih operacija.
• Dizajnirao i isporučio sučelje analitičkih widgeta - korisnici su mogli konfigurirati, mijenjati veličinu i interagirati s nadzornim pločama operativnih podataka uživo.
• Primijenio strategije predmemoriranja i optimizacije performansi na frontend i backend, poboljšavajući vremena učitavanja nadzornih ploča i brzinu obrade podataka.
• Dizajnirao i izgradio opću arhitekturu aplikacije, skalirao platformu s rastućim zahtjevima i donosio ključne tehničke odluke za pouzdanost i mogućnost održavanja.
• Pisao jedinične testove i integracijske testove (Jest, React Testing Library) postigavši 80% pokrivenosti testovima.
• Proširio platformu modulima React Native za terenske tehničare, omogućujući mobilni pristup osnovnim tijekovima rada.

Kliknite za istraživanje tehnologije

• 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 za istraživanje tehnologije

• 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 za istraživanje tehnologije

• 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 za istraživanje tehnologije

• 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 za istraživanje tehnologije

• 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 za istraživanje tehnologije