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Denis User

@denisuser13

Senior Frontend Engineer at BrainRocket who improved Lighthouse scores to 80–90+ and built an internal back-office platform.

Portugal

Message

At BrainRocket, I contributed to product launches, built an internal back-office platform, and improved accessibility across company websites with WCAG. I also optimized image loading and code, raising Lighthouse scores to 80–90+ on mobile and desktop.

At CXM Group, I built React and TypeScript interfaces for a Forex and crypto trading platform and improved database interaction speed by 2.6x. Across FinTech and other web products, I’ve raised Lighthouse scores as high as 85–100 and increased unit test coverage from 5% to 57%.

Experience

Work history, roles, and key accomplishments

Senior Frontend Engineer

BrainRocket

Apr 2025 - Sep 2026 (1 year 5 months)

Contributed to key product launches using React, Angular, and TypeScript, driving high user engagement. Improved accessibility by implementing WCAG, built an internal back-office platform, and optimized image loading and codebase to raise Lighthouse scores from 50-60 to 80-90+.

React Angular TypeScript WCAG Lighthouse CI CD API Integration Technical Documentation

Senior Frontend Engineer

CXM Group

Jan 2024 - Jan 2025 (1 year)

Built responsive React/TypeScript interfaces with Redux, ensuring stable performance across devices and accurate Figma implementation. Refactored PHP/MySQL database structure and queries, improving database interaction speed by 2.6x, and optimized Nginx and PHP configuration to improve page load speed by more than 85%.

React TypeScript Redux Figma PHP MySQL Nginx LESS JavaScript CoffeeScript jQuery

Senior Frontend Engineer

Libertex Group

Oct 2022 - Jan 2024 (1 year 3 months)

Built responsive interfaces with React, TypeScript, and SCSS/SASS, ensuring stable performance across devices. Raised unit test coverage from 5% to 57% by writing and maintaining a Jest test suite, and improved application performance and stability by 13-27% through React/JavaScript optimization.

React TypeScript SCSS SASS Jest Redux REST APIs Code Review Agile

Senior Frontend Engineer

Lincoln Labs, Inc

Aug 2020 - Oct 2022 (2 years 2 months)

Built scalable web applications using React, TypeScript, AWS, and Docker. Improved Core Web Vitals, raising Lighthouse scores from 40-60 to 85-100 across mobile and desktop, and used AWS and Python automation to speed up feature delivery by 53%.

React TypeScript AWS Docker Core Web Vitals Lighthouse Python Figma Technical Interviewing Onboarding

Fullstack Software Engineer

Versality

Mar 2018 - Aug 2020 (2 years 5 months)

Developed and maintained client websites using JavaScript, PHP, and MySQL. Built a reusable module library that increased project delivery speed by 33%, integrated frontend applications with backend systems via RESTful APIs, and optimized page load speed.

JavaScript PHP MySQL REST APIs Module Library Client Communication

Fullstack Software Engineer

Penoprofil

Nov 2015 - Feb 2018 (2 years 3 months)

Developed and optimized the company website end-to-end, helping it reach the top five Google search results. Improved server-side performance and loading stability using technical SEO and Google Analytics, and simplified technical processes so non-technical staff could complete 50%+ of related tasks without engineering support.

Technical SEO Google Analytics Server Side Performance Process Simplification

Fullstack Software Engineer

Earlier Project Work

Delivered 50+ client projects, including custom CMS platforms, product-selection systems, cost calculators, and automated SEO tools. Built applications using PHP, MySQL, JavaScript, HTML, CSS, RESTful APIs, and the MVC pattern.