Available to hire
Hi, I’m Karol Piotrowski, a Senior Full Stack Developer with 11 years of experience delivering high-performance, responsive corporate websites and enterprise-grade digital platforms for B2B consulting and technology-focused industries. I’m proficient in HTML5, CSS3, JavaScript, and WordPress, with a strong emphasis on UX/UI design, SEO optimization, and performance tuning. I excel at translating complex regulatory and technical content into intuitive digital experiences that drive engagement and credibility.
I love crafting clean architectures and maintainable systems for long-term growth. Collaborating with cross-functional teams, I focus on scalable front-end and back-end solutions, data-driven UX improvements, and robust documentation to empower ongoing development and future features. When I’m not coding, I enjoy refining design systems, optimizing Core Web Vitals, and sharing knowledge to help teams deliver delightful products.
Skills
Language
English
Fluent
Work Experience
Senior Web Developer at Darly Solutions
April 1, 2021 - PresentSpearheaded website redesign projects, enhancing visual appeal and improving user engagement metrics by over 35%. Optimized site performance using HTML, CSS, and JavaScript, reducing page load time by 42%. Implemented responsive design strategies across all web applications, increasing mobile traffic retention by 50%. Conducted comprehensive SEO audits to identify technical issues, keyword opportunities, and content gaps. Integrated on-page SEO strategies, including internal linking and metadata optimization, boosting search engine ranking by ~30%. Led the migration of legacy websites to WordPress, ensuring modern, secure, and scalable site architecture. Collaborated with content teams to optimize multimedia assets, resulting in 25% faster page rendering. Designed and implemented UX/UI improvements based on user behavior analytics, raising average session duration by 20%. Developed custom JavaScript solutions to enhance interactivity (dynamic forms, sliders, content toggles). Set up Go
Software Engineer at Infolet
August 1, 2018 - March 1, 2021Developed and maintained dynamic web applications using HTML, CSS, and JavaScript; optimized website performance by reducing load time by 35% through asset compression and caching strategies. Designed responsive web layouts, increasing mobile user engagement by 40%. Implemented on-page SEO improvements, including metadata optimization and keyword integration. Collaborated with design teams to revamp user interfaces and enhance user experience across multiple projects. Conducted site audits to identify bugs, accessibility issues, and SEO gaps. Developed reusable JavaScript components to streamline front-end development and reduce maintenance effort. Integrated analytics tracking tools to monitor KPIs and site performance metrics. Supported migration of client websites to CMS platforms, improving content management efficiency. Delivered customized interactive features to boost visitor engagement.
Software Engineer at Zaven
October 1, 2015 - July 1, 2018Designed and developed client-facing websites using HTML, CSS, and JavaScript; implemented responsive design techniques, enhancing mobile accessibility by 35%. Conducted SEO optimization for multiple client projects, achieving higher search rankings and traffic. Integrated analytics tools to provide actionable insights for site improvements. Participated in the migration of websites to WordPress and other CMS platforms. Optimized images and media assets to improve site speed and performance. Provided technical recommendations for UI/UX improvements to boost overall user satisfaction.
Front End Engineer at Consensys
June 1, 2021 - PresentDelivered end-to-end PayHip front-end implementations across multi-page digital product sites, translating provided mockups into clean, conversion-optimized HTML, CSS, and JavaScript with zero backend dependencies. Implemented 12–14 page front-end scopes with consistent visual systems, ensuring typography, spacing, color usage, and component behavior remained uniform across all customer touchpoints. Customized PayHip product pages using platform-supported markup and styling techniques, enhancing perceived product value while maintaining full compatibility with hosted checkout flows. Applied responsive design principles to guarantee reliable rendering across desktop, tablet, and mobile breakpoints, improving engagement metrics and reducing bounce rates. Integrated light JavaScript logic for UI interactions, dynamic content toggles, and usability enhancements without introducing unnecessary complexity or performance overhead. Optimized front-end assets and stylesheets to improve load t
Software Engineer at UCB
June 1, 2018 - April 1, 2021Executed front-end-only implementations for hosted and embedded storefronts, emphasizing HTML, CSS, and JavaScript solutions over custom backend development. Transformed high-fidelity mockups into production-ready layouts with meticulous attention to spacing, alignment, and visual rhythm. Styled hosted product pages to align with brand identity while respecting platform limitations and avoiding unsupported customizations. Developed reusable CSS patterns to maintain consistency across large multi-page marketing and product experiences. Implemented lightweight JavaScript interactivity and ensured accessibility-friendly markup and keyboard navigation. Coordinated delivery timelines independently, managing parallel page builds without sacrificing quality or consistency. Improved perceived product credibility through structured content layouts and strategic use of trust indicators. Reduced layout regressions by enforcing strict CSS organization and naming conventions. Tested implementations
Software Developer at Razor Ltd
March 1, 2014 - May 1, 2018Built static and hosted-platform front-end experiences focused on digital product presentation and conversion clarity. Converted design assets into semantic HTML structures supporting long-term maintainability and accessibility. Authored modular CSS architectures enabling consistent styling across expanding page sets. Implemented responsive layouts optimized for mobile-first digital commerce audiences. Added targeted JavaScript enhancements to improve interaction feedback and content discoverability. Ensured visual fidelity between design mockups and final renderings through detailed QA processes. Supported hosted e-commerce constraints by prioritizing supported customization techniques over intrusive workarounds. Improved user trust through clean layouts, predictable navigation patterns, and professional visual hierarchy. Maintained fast load times by minimizing asset weight and avoiding unnecessary dependencies. Delivered complete front-end scopes independently using provided specifi
Senior Full Stack Engineer at ConsenSys
June 1, 2021 - PresentArchitected and delivered highly interactive React-based web applications, leveraging JavaScript, HTML5, and CSS3 to improve user engagement across multiple digital education and community platforms. Engineered interactive modules using Canvas API and WebGL, implemented responsive design with React and TypeScript, and collaborated with product designers to translate educational objectives into intuitive interfaces. Developed REST APIs with Node.js/Express, optimized performance, accessibility, and CI/CD pipelines; mentored junior developers.
Software Developer at Razor LLC
March 1, 2014 - May 1, 2018Created dynamic web-based applications with JavaScript, HTML5, CSS3; built interactive modules with gamification; designed responsive layouts with CSS Grid/Flexbox; integrated back-end services via Node.js/Express REST APIs; performed cross-browser testing and accessibility improvements; documented code and collaborated with clients.
Senior Full Stack Developer (Remote) at Consensys
June 1, 2021 - PresentLed the design and development of responsive corporate websites using HTML5, CSS3, JavaScript, and WordPress. architected scalable front-end systems with reusable components, translated blockchain and regulatory service offerings into structured, accessible content, and implemented advanced SEO and performance strategies that increased organic traffic by about 45%. Implemented high-performance forms with robust validation to improve lead capture. Optimized performance with lazy loading, caching, and Core Web Vitals improvements, achieving sub-two-second load times across major browsers and devices. Collaborated with stakeholders to align messaging with regulatory standards and developed custom WordPress themes and plugins for dynamic content delivery. Led usability testing to enhance navigation and accessibility, established documentation frameworks for maintenance and future feature integration, and integrated analytics to support data-driven UX and SEO optimization. Drove cross-funct
Software Developer at Razor Lnc
March 1, 2014 - May 1, 2018Developed and deployed responsive corporate websites for consulting and technical clients using HTML5, CSS3, JavaScript, and CMS platforms. Focused on UX/UI design, ensuring intuitive navigation and clear presentation of complex services. Built foundational SEO, interactive forms, and optimized front-end performance. Maintained and customized CMS-based sites, conducted usability testing, and created reusable UI components to streamline development across multiple projects. Supported deployment pipelines with Git and produced detailed architectural and maintenance documentation.
Education
Bachelor of Computer Science at Singapore Management University
January 1, 2010 - January 1, 2014Bachelor of Computer Science at Nanyang Technological University, Singapore
January 1, 2011 - January 1, 2015Bachelor of Computer Science at Nanyang Technological University, Singapore
January 1, 2011 - January 1, 2015Bachelor of Computer Science at Nanyang Technological University, Singapore
January 1, 2011 - January 1, 2015Qualifications
Industry Experience
Software & Internet, Professional Services, Media & Entertainment, Education, Healthcare, Life Sciences
Skills
Hire a Web Developer
We have the best web developer experts on Twine. Hire a web developer in Lublin today.