Женя

Yevhenii Kielariev
Kyiv, Ukraine | Open to Remote EU / UK / US | [відкрити контакти](див. вище в блоці «контактна інформація») | [відкрити контакти](див. вище в блоці «контактна інформація») | linkedin.com/
in/yevhenii-kielariev | Telegram: @Zhenia_Kielariev

SUMMARY
Full Stack Engineer with 7 years of experience building scalable SaaS, enterprise, and customer-facing web
applications using React, Next.js, TypeScript, and Node.js. Experienced in delivering end-to-end product features,
developing REST APIs, integrating third-party services, and building high-performance web applications.
Strong background working closely with Product Managers, Designers, QA, and Engineering teams to deliver data-
driven product improvements. Hands-on experience with product analytics, event tracking, feature experimentation, A/
B testing, and feature flags. Skilled in web performance optimization, Core Web Vitals improvements, and technical
SEO to enhance user engagement, conversion, and overall product performance. Comfortable taking ownership of
complex features from design through deployment while contributing to engineering best practices.

EDUCATION
Zhytomyr State Technological University
Bachelor's Degree in Telecommunications

EXPERIENCE
Senior Full Stack Engineer (Frontend-Focused) Jan 2024 – Present
Olimp Digital
Tech Stack: React, TypeScript, Node.js, Express.js, React Query, REST APIs, React Native, Ant Design, Storybook,
Jest, GA4, Mixpanel, PostHog, CI/CD
• Led development of end-to-end product features across React frontends and Node.js backend services,
contributing from technical design through production deployment.
• Developed scalable APIs and integrated third-party services supporting business-critical workflows for
enterprise customers.
• Implemented product analytics and event tracking using GA4, Mixpanel, and PostHog to enable data-driven
product decisions and feature evaluation.
• Supported A/B testing and feature experimentation initiatives by implementing tracking, analysing product
metrics, and iterating based on insights.
• Collaborated closely with Product Managers and Designers to translate growth goals into high-impact features
while balancing technical and business priorities.
• Improved application performance through rendering optimization, lazy loading, code splitting, and Core Web
Vitals enhancements.
• Contributed to technical SEO improvements for React and Next.js applications, improving performance,
crawlability, and user experience.
• Established reusable architecture, shared UI components, and engineering standards to improve maintainability
and delivery speed.
Senior Frontend Engineer Oct 2021 – Dec 2023
Kyivstar
Tech Stack: React, TypeScript, Node.js, Redux, React Query, React Native, REST APIs, GA4, CI/CD
• Developed scalable enterprise applications supporting high-volume operational workflows and business-critical
internal systems.
• Built complex React modules and integrated backend services through REST APIs while collaborating closely
with backend engineering teams.
• Implemented analytics tracking (GA4) and contributed to A/B testing initiatives to improve user flows,
conversion, and product performance.

• Worked closely with Product Owners, business stakeholders, and QA teams to deliver features aligned with
business objectives.
• Optimized rendering performance, frontend architecture, and application responsiveness across multiple
enterprise products.
• Participated in technical discussions, feature planning, estimation, and Agile delivery processes.
Frontend-Focused Full Stack Engineer Apr 2019 – Oct 2021
PixelTeh
Tech Stack: React, Next.js, TypeScript, Node.js, React Native, React Query, Material UI, REST APIs
• Built SaaS, AI-driven, and e-commerce applications using React, Next.js, and Node.js, delivering complete
end-to-end product functionality.
• Developed SEO-friendly Next.js applications using SSR and SSG to improve discoverability and user
experience.
• Integrated third-party APIs, analytics platforms (GA4, PostHog), and external business services across multiple
products.
• Supported feature flag implementations for controlled feature rollouts and safer product experimentation.
• Improved Core Web Vitals, Lighthouse scores, and frontend performance through modern optimization
techniques.
• Collaborated with designers and product stakeholders to rapidly validate ideas and deliver scalable business
features.
• Developed shared business logic across web and mobile applications using React Native.

TECHNICAL SKILLS
Frontend: React, Next.js, TypeScript, JavaScript (ES6+), React Query, Redux, React Native
Backend: Node.js, Express.js, REST APIs, GraphQL
Product Engineering: Feature Development, Product Analytics, Event Tracking, A/B Testing, Feature Flags, Growth
Experiments
Analytics: Google Analytics 4 (GA4), Mixpanel, PostHog, Google Tag Manager
Architecture: Full Stack Development, Scalable Web Applications, Design Systems, SSR/SSG, State Management,
Component-Driven Development
Performance: Core Web Vitals, Lighthouse Optimization, Technical SEO, Code Splitting, Lazy Loading, Rendering
Optimization
APIs & Integrations: REST APIs, Third-Party Integrations, CMS Integrations, API Design, Data Modeling
Testing: Jest, React Testing Library
UI: Ant Design, Material UI, Storybook, Accessible UI
Tools: Git, GitHub, GitLab, CI/CD, Webpack
Methodologies: Agile/Scrum, Cross-functional Collaboration, Product Development

LANGUAGES
English — Upper-Intermediate (B2) Ukrainian — Native Russian — Native