Andrey Kotko

Senior Frontend Engineer

kotkoa@gmail.com	residence: Spain + work-permit	+34-647-185-406
Linkedin	Github	Twitter
Telegram: @Kotkoa	Download CV	Online CV

ABOUT ME

Senior Frontend Engineer with 6+ years of commercial experience building production web applications with React, TypeScript, and Next.js. Specialized in AI-powered SaaS products, real-time data interfaces (GraphQL/Apollo Client), and scalable design systems.

Recent focus: frontend for AI products — built the core web application for an AI-powered digital clone platform (CloneForce), integrating voice AI (ElevenLabs), real-time GraphQL subscriptions, and OAuth flows for third-party services.

Deep Apollo Client expertise: custom cache strategies, type policies, AC3→4 migration, WebSocket subscriptions. Strong background in design systems (4 projects: Yara International, HCX, Bridge The Gap, CloneForce), performance optimization (40% load time reductions), testing culture (Jest, Cypress, Playwright), and CI/CD integration.

Experience across startup, scale-up, and enterprise environments with fully distributed international teams.

Based in Pego, Spain. Available for remote roles across Europe (CET/CEST timezone).

TECHNICAL SKILLS

Frontend: React, TypeScript, JavaScript ES6+, Next.js (SSR/SSG), HTML5, CSS3
State Management: Redux, Redux Toolkit, Jotai, MobX, React Context
Styling & Design Systems: MUI, Tailwind, SASS, Styled Components, Storybook, Radix UI, Design Tokens
APIs & Data: Apollo Client/GraphQL, GraphQL Subscriptions, REST APIs
Testing: Jest, Cypress, Playwright, React Testing Library
Build & DevOps: Webpack, Vite, Git, CI/CD Pipelines, ESLint, Prettier
AI & Integrations: ElevenLabs SDK, OpenAI API, OAuth (Microsoft, Google, HubSpot)
Other: i18n, Accessibility (WCAG), Agile/Scrum, Nx Monorepo, Figma

EXPERIENCE

FullStack Engineer - Contractor

CloneForce, Newport Beach, California, United States (Remote)
November 2024 – March 2026

FullStack Engineer on CloneForce cloneforce.com an AI-powered digital clone platform that creates personalized AI assistants and coaches powered by OpenAI, Pinecone (RAG), and ElevenLabs, deployed across Slack, MS Teams, and web channels. Developed frontend interfaces for real-time human-AI interactions, conversational voice experiences, and automation workflows within the core web application.

Developed real-time AI interaction interfaces using GraphQL subscriptions and streaming updates, enabling conversational clone experiences with live AI responses.
Built and maintained a reusable UI component library with 50+ MUI-based components, improving visual consistency across the platform.
Integrated ElevenLabs voice chat through the React SDK, replacing the default embed widget with a custom implementation for greater control over the conversational voice UI.
Implemented real-time updates using GraphQL subscriptions (graphql-ws), enabling live clone interactions and streaming AI responses.
Built OAuth integration flows for Microsoft, Google, and HubSpot, allowing clone skills to securely connect with external platforms on behalf of users.
Improved frontend development workflows with strict TypeScript, ESLint, GitHub branch protections, and standardized architecture patterns to maintain consistent code quality.
Improved page load performance by 1.2s through code splitting, lazy loading, and Apollo Client cache optimization.
Implemented comprehensive Cypress E2E testing covering critical user flows across the AI assistant interface.

Tech Stack: React, Next.js (SSR), TypeScript, Jotai, Tailwind, SASS, MUI, Apollo GraphQL, GraphQL Subscriptions, ElevenLabs React SDK, Webpack, Jest, Cypress, Git

FullStack Engineer

On the Beach, Manchester, England, United Kingdom (Remote)
April 2025 – October 2025

FullStack Engineer in a UK-based team to modernize and support the On the Beach holiday platform onthebeach.co.uk. The role involves working with a large legacy codebase, focusing on refactoring, component modernization, and improving maintainability, performance, and developer experience.

I collaborate with UK colleagues to deliver new features and experiments using JavaScript, TypeScript, GraphQL, React 19, and Next.js 15, employing feature flags for controlled rollouts and quick reversions. My work spans frontend optimization, API integrations, and user experience enhancements, contributing flexibly across multiple areas of the platform.

As part of the Shop XP team, I’ve led and contributed to several key initiatives, including:

Upgrading the Booking Flow technology stack to the latest React 19 and Next.js 15, improving performance, security, and engineering efficiency.
Migrating from Apollo Client 3 to Apollo Client 4, enhancing data management, caching performance, and overall stability.
Implemented feature flags for controlled rollouts and A/B experimentation, enabling data-driven UI decisions across 3 concurrent experiments.
Implementing new UI toggle features, refining default search logic, and expanding tracking coverage for analytics and experimentation.

These improvements have resulted in faster page loads, smoother navigation between search and deal detail pages, and a more reliable, scalable foundation for future development.

Tech Stack: JavaScript ES6+, TypeScript, React 19, Next.js 15 (SSR/SSG), MobX, Apollo Client 4, GraphQL, Webpack, Git

Fullstack Engineer - Contractor

Netguru | B Corp™, Poznan, Poland (Remote)
April 2025 – October 2025

Worked as a contract Fullstack Engineer through Netguru netguru.com, contributing to international client projects using Next.js, TypeScript, JavaScript, and Apollo GraphQL.

Tech Stack: Next.js, JavaScript ES6+, Apollo GraphQL, TypeScript

Frontend Engineer - Contractor

Human Capital Exchange (HCX), Los Angeles (Remote)
September 2022 – January 2025

Developed an HCX trading platform for a new equity-based asset class using React, TypeScript, GraphQL, Jotai, and Jest.

Configured a CI/CD pipeline with Jest unit tests and Cypress E2E integration, achieving 80%+ test coverage for critical user flows, reducing regression bugs by 35%, and decreasing manual QA effort through automated user flow validation.
Streamlined account setup flows for multiple user types by integrating JSON Forms, Yup validation, and Apollo GraphQL, significantly improving onboarding and form completion flows.
Collaborated with the backend team to extend and improve API integrations, adding new features and resolving issues that improved server performance by 20% and accelerated feature delivery by 25%.
Simplified the payment architecture by removing three blockchain libraries, migrating to bank transactions, and implementing debit/credit card and bank account functionality, reducing operational costs by 30%.
Integrated DocuSign for in-app application signing, streamlining document workflows, reducing turnaround time by 40%, and supporting KYC and legal compliance requirements.
Contributed to onboarding documentation and developer integration processes, helping reduce onboarding time from one month to one week.
Enhanced the global Material-UI theme system by consolidating shared styles and reusable patterns, reducing component development time and saving approximately 68 engineering workdays.

Tech Stack: React, TypeScript, Jotai, Material-UI, GraphQL, Next.js, Jest, Cypress

UI Engineer

Yara International, Singapore (Remote)
August 2023 – January 2024

Hired to enhance the usability and accessibility of Yara International’s design system, focusing on creating new components and refactoring existing ones, utilizing designs by our team of designers on Figma. This role required technical proficiency and design skills to develop components within the company’s React-based design system. The project was managed in a Git repository with NxMonorepo, consolidating web (React) and mobile (React Native) libraries for developers.

Enriched a React library with over 10 new components, and refactored existing ones, improving accessibility to meet global WCAG standards, boosting compliance by 44%.
Conducted an accessibility audit and initiated improvements, ensuring the components meet global accessibility standards.
Updated design system documentation to Storybook@7, optimizing infrastructure, and overhauling documentation for improved clarity and utility.
Developed a new token structure to streamline design-to-code workflows, facilitating easier adoption of design principles and more consistent implementation across projects.
Team Collaboration: Worked closely with designers to refine and implement component designs, discussing the overall look of the Storybook theme.
Quality Assurance: Implemented rigorous code review and testing protocols to ensure component reliability across various browsers and devices, addressing bugs promptly to maintain system integrity.

Tech Stack: React, TypeScript, Storybook, Radix UI, Figma, Design Systems, Design Tokens, Accessibility (WCAG), GitHub, React Native

Frontend Engineer

Bridge The Gap, Europe (Remote)
December 2022 – September 2023

I was recruited as a Frontend and UI developer to join Bridge the Gap, a European-based team of developers led by Varia Stepanova, to enhance the team’s capabilities. This role enabled me to combine my technical expertise with a keen sense of design, contributing significantly to our digital systems.

Maintained a Next.js website, migrating the platform from Next.js 12 to 14.
Updated the design system npm library with new reusable React components.
Migrated the web application from Gatsby 3 to Gatsby 5, improving compatibility, maintainability, and build performance.
Refactored project components to improve performance and maintainability, including upgrading dependencies such as @mdx-js/react, improving code quality with ESLint and Prettier, and enhancing UI components and image rendering across web pages.
Contributed to the design system npm library by implementing major updates to the ProfileCard component across multiple releases, improving layout styling, UI consistency, and component functionality.

Tech Stack: React.js, Next.js, GatsbyJS, Jest, Tailwind CSS, Figma, Design Systems

Frontend Developer

Root Name System (RNS), Singapore (Remote)
November 2021 – July 2022

Hired in international tech team as a frontend developer to enhance and manage their innovative digital identity platform, rns.id (Root Name System). The project aimed to develop an application by issuance of digital IDs of digital residence islands of Palau. My role was on optimizing and redesigning web applications, integrating new features of Document verifications, and elevating quality through measures such as Sentry.io logging, TypeScript migration, and Jest test coverage. A key part of my responsibilities included fast-forward landing page creation to meet marketing team goals.

Developed 3 landing pages, 2 web apps, and 35 HTML email templates for user subscriptions, improving user engagement and implementing features such as ID verification, TypeScript migration, and Jest test coverage.
Refined MaterialUI components into Styled Components, improving UI flexibility and responsiveness; decreased app load time by 40% and increased user satisfaction ratings by 15%.
Managed complex application state using Redux and Redux Toolkit; later migrated state management to MobX, reducing boilerplate by 40% and improving maintainability across the application.
Implemented multi-site (multizone) experience (SSR and SPA) as one web app for developing both websites independently with the same level of control.
Integrated internationalization using i18n, enabling localization for 12 new languages and contributing to a 28% increase in global user engagement.

Tech Stack: React.js, Next.js (SSR), TypeScript, JavaScript ES6+, Tailwind, SASS, Redux, Redux Toolkit, MobX, Material-UI, Styled Components, i18n, Jest, Webpack, S3, Git

Freelance Javascript Developer (React.JS & Node.JS)

Freelance, Tenerife, Spain (Remote)
January 2020 – December 2021

I was acting as a full-stack engineer, creating services and endpoints with Express and frontend logic with React. I was responsible for the development of a web application for a local business. The application was built with React, Redux, and Node.js, and was designed to be responsive and accessible across various devices.

Integrated Javascript Playground for creating sandboxes with the ability to run and check code snippets without any need for deployment
Migrated to clean React with Context API
Frontend with React/Redux
RESTful API’s Node.js and Express
Implemented low-level CSS framework Tailwind

Account Manager of Microstocks and Analytic
Kotkoa.com - a family business
From Jun 2012 to Jun 2020 I used my JavaScript capabilities to create scripts that simplified the management of over 20 stores, allowing for centralized control. I used my CMS management expertise to improve and maintain the WordPress based home page, along with optimizing SEO through strategic keyword and tag descriptions. Technologies Used: WordPress, HTML, CSS, SEO

Maintenance of 20 stores with content updating
Compiling lists of selling keywords
Sales analysis
The leadership of a small team of 4 employees

Project Manager Ramotion.com, Ukraine From Sep 2010 to May 2013

Managing the iOs projects and contributing to the AppStore.

Account manager
Studio3dlife.com, Ukraine
From Jan 2009 to Aug 2010

Managing of own startup
Training and coaching employees
Communicating with customers

Html-CSS Developer
AllDevelop.com, Sevastopol, Ukraine
From Sep 2008 to Jan 2010

Creating HTML markup templates
Updating and modifying existing CSS code
Maintenance HTML content daily
Processing data in a content

3d graphic designer Svelio, Sevastopol, Ukraine From May 2004 to Aug 2008

3D Design & Rendering: Developed interior design projects and architectural renderings using 3ds Max.

EDUCATION

Bachelor’s Degree in Instrument Engineering

Sevastopol State Technical University, Ukraine
1999 – 2004

LICENSES & CERTIFICATIONS

Claude Code: Professional AI Setup – Frontend Masters (2025)

LANGUAGES

English: Fluent (B2+)
Ukrainian: Native
Russian: Native
Spanish: Conversational

PORTFOLIO

Bitcoin Testnet Wallet – Minimalist Bitcoin wallet using React.js, Next.js, and Redux Toolkit.
Simple Auth App – Secure authentication app with OAuth integration (Google & Microsoft).
Rick and Morty Explorer – Character browser using GraphQL API, React, and TypeScript.
Email Newsletter Template – Responsive email template for event notifications.
Weight Converter – Web app to convert weight between metric and imperial units.

Check-in & Version Log

This section is for a simple check-in—just updating the version to mark my presence and keep the GitHub contribution graph green.

Current version: v1.02.12