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Hi, I’m Valentin Yefimov, a Senior Full-Stack Engineer with 16+ years of experience building high-performance web applications from MVPs to enterprise-scale SaaS. I excel at turning complex product ideas into solid architectures and reusable components, especially in React/Next.js ecosystems, with a strong focus on performance, accessibility, and developer experience. I enjoy mentoring teams, writing robust tests, and shaping platform foundations that scale for growth. When I’m not coding, I mentor engineers, contribute to AI/SDLC tooling, and help drive product clarity through thoughtful design and architecture. I’m comfortable spanning frontend and backend work, collaborating with product and design to deliver impactful software from concept to production.…Hi, I’m Valentin Yefimov, a Senior Full-Stack Engineer with 16+ years of experience building high-performance web applications from MVPs to enterprise-scale SaaS. I excel at turning complex product ideas into solid architectures and reusable components, especially in React/Next.js ecosystems, with a strong focus on performance, accessibility, and developer experience. I enjoy mentoring teams, writing robust tests, and shaping platform foundations that scale for growth. When I’m not coding, I mentor engineers, contribute to AI/SDLC tooling, and help drive product clarity through thoughtful design and architecture. I’m comfortable spanning frontend and backend work, collaborating with product and design to deliver impactful software from concept to production.

Valentin Yefimov

Full Stack Developer, Front-End Developer, Back-End Developer, +2

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Hi, I’m Valentin Yefimov, a Senior Full-Stack Engineer with 16+ years of experience building high-performance web applications from MVPs to enterprise-scale SaaS. I excel at turning complex product ideas into solid architectures and reusable components, especially in React/Next.js ecosystems, with a strong focus on performance, accessibility, and developer experience. I enjoy mentoring teams, writing robust tests, and shaping platform foundations that scale for growth. When I’m not coding, I mentor engineers, contribute to AI/SDLC tooling, and help drive product clarity through thoughtful design and architecture. I’m comfortable spanning frontend and backend work, collaborating with product and design to deliver impactful software from concept to production.…Hi, I’m Valentin Yefimov, a Senior Full-Stack Engineer with 16+ years of experience building high-performance web applications from MVPs to enterprise-scale SaaS. I excel at turning complex product ideas into solid architectures and reusable components, especially in React/Next.js ecosystems, with a strong focus on performance, accessibility, and developer experience. I enjoy mentoring teams, writing robust tests, and shaping platform foundations that scale for growth. When I’m not coding, I mentor engineers, contribute to AI/SDLC tooling, and help drive product clarity through thoughtful design and architecture. I’m comfortable spanning frontend and backend work, collaborating with product and design to deliver impactful software from concept to production.

Available to hire

Hi, I’m Valentin Yefimov, a Senior Full-Stack Engineer with 16+ years of experience building high-performance web applications from MVPs to enterprise-scale SaaS. I excel at turning complex product ideas into solid architectures and reusable components, especially in React/Next.js ecosystems, with a strong focus on performance, accessibility, and developer experience. I enjoy mentoring teams, writing robust tests, and shaping platform foundations that scale for growth.

When I’m not coding, I mentor engineers, contribute to AI/SDLC tooling, and help drive product clarity through thoughtful design and architecture. I’m comfortable spanning frontend and backend work, collaborating with product and design to deliver impactful software from concept to production.

Skills

Experience Level

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Intermediate

Intermediate

Intermediate

Intermediate

Intermediate

Intermediate

Intermediate

Language

Ukrainian

Fluent

English

Advanced

Russian

Advanced

Work Experience

Senior Full-Stack Engineer at Merly

September 1, 2024 - Present

Senior Full-Stack JS Staff Engineer responsible for platform-wide performance and quality improvements across Merly Mentor product. Led optimizations such as reducing page load times, introducing skeleton loaders, and implementing end-to-end tests to improve release confidence and user experience. Built Chakra UI-driven UI blocks and React/Next.js acceleration strategies, and led a team of engineers through full product lifecycle.

Lead Design and Delivery at Platflow.ai

May 1, 2023 - September 1, 2024

Led the design and delivery of the Platflow.ai MVP, an AI-powered SaaS for clinicians, including architecture, RBAC, activity tracking, and multi-tenant user management. Built full-stack features, re-architected components for rapid iteration, and established long-term platform strategy.

Full Stack Developer (PHP/JS) at Gameloft

June 1, 2010 - February 1, 2012

Built high-traffic internal tools across Gameloft’s global offices focused on reliability, data integrity, and real-time responsiveness. Implemented full-stack solutions using PHP/JS, designed scalable backend services and robust frontend interfaces.

Full Stack Developer (PHP/JS) at Gameloft, Ukraine

June 1, 2010 - February 1, 2012

Built high-traffic internal enterprise tools for thousands of daily users across Gameloft’s global offices, focusing on reliability, data integrity, and real-time responsiveness. Designed and implemented a company-wide Meeting Room Booking System; implemented authentication and role-based access control integrated with LDAP; pioneered SPA approaches using ExtJS/YUI to deliver desktop-class UX in the browser. Designed and optimized MySQL schemas for performance, implemented PHP business logic to support scheduling workflows, and collaborated with stakeholders to evolve product systems and a company-wide recruitment assessment platform.

Lead / Senior Front-End Developer (PHP/JS) at Gameloft, Ukraine

February 1, 2012 - February 1, 2018

Led design and delivery of mid-tier and front-end systems; managed cross-functional front-end and back-end teams of up to 12 engineers; established clean API contracts and robust data flows. Orchestrated SPA architecture during a period when single-page apps were emerging, delivering highly interactive, desktop-class UX in the browser. Implemented robust error handling, improved data validation, and contributed to architectural decisions that scaled across multiple products. Pioneered multi-team collaboration and contributed to global hiring assessments and platform initiatives.

Senior Full-Stack JS Engineer at Merly, USA

September 1, 2023 - September 1, 2024

Led design and delivery of the Platform Flow.ai MVP from scratch, a health-care Chrome/Edge extension enabling clinicians to retrieve patient information directly within their browser workflows, supporting early-stage fundraising.

Senior Full-Stack Engineer at Merly, USA

September 1, 2024 - Present

Drove platform-wide performance and quality improvements across the Merly Mentor product, contributing to both technical excellence and developer experience. Rebuilt the browser extension from vanilla JS to a React-based solution, achieving faster development cycles and a more robust UI. Implemented Redux for global state management, introduced Chakra UI for consistent UI primitives, and expanded unit and integration coverage to reduce regressions.