<YURI SEMENENKO />

Based in Krakow, Poland

Yuri Semenenko

Senior Frontend Engineer, Mentor & Trainer — Tech Lead Scope

Available for remoteLooking for interesting projectsOpen to mentoring
Download CVContact meView experience

01 / About

About

I help teams modernise frontend platforms, raise engineering quality, and ship scalable React applications. Fourteen years across FinTech, SaaS, CMS, and enterprise products — combining hands-on engineering with technical leadership, mentoring, and frontend education.

Highlights

  • 14+ years building production React platforms
  • 20% perf gain refactoring legacy Ember.js at Monterosa
  • 500+ students trained over 8 years at IT Academy
  • Manager-vouched by CTOs and Engineering Leads

02 / Experience

Experience

  1. StoneX Group Inc.

    Nov 2024 — Present

    Front-end Engineer

    Business-critical FinTech platform at a NYSE-listed institutional brokerage serving multi-asset traders. Built on legacy Sitecore CMS, .NET, native JavaScript and Preact, mid-migration to a modern React / Next.js / Tailwind stack across three frontend squads. Joined mid-stage — platform architecture was already set; my focus is landing component-level migration and reliability of the new stack.

    Outcome

    • Migrated 10-15 major components (skeletons, tables, composite molecules) to the new stack — base atoms not included.
    • Shipped internal Lightstreamer SDK client adopted by multiple components for real-time data flow.
    • Defended and shipped ~5 of ~8 POCs in six months (~60% adoption rate).
    • Review 2-4 PRs per day as a required reviewer — gating quality at merge time.
    Role
    • Frontend engineer in a 4-developer + 2-QA squad.
    • Own migration of major UI components from the legacy stack to React / Storybook / Tailwind.
    • Built and maintain an internal client wrapping the Lightstreamer SDK for real-time data, used across multiple components.
    • Act as one of the core required reviewers — without my +1, code does not merge.
    • Mentor 1-2 juniors and currently organising a company-wide frontend community spanning 4+ technical teams across multiple offices and countries.
    • React
    • Next.js
    • TypeScript
    • Tailwind CSS
    • Storybook
    • Lightstreamer SDK
    • Sitecore CMS
    • .NET
    • Preact
    • Uniform.dev
    • Kontent.ai
    • GitHub
    • Vercel

  2. Synder

    Nov 2023 — Sep 2024

    Senior Front-end Engineer

    Synder is a Y-Combinator-backed FinTech B2B SaaS automating accounting workflows for QuickBooks, Xero and payment-platform integrations. Senior FE role across four microfrontend products built on different React versions, with inconsistent component states and varying levels of implementation. The product needed both day-to-day delivery and longer-term consolidation of frontend standards.

    Outcome

    • ESLint overhaul (automated import sorting + stricter validation rules) cut PR review cycle by 30-40%.
    • Component Library proposal accepted by leadership; established working channel with the design team and shipped first demo components.
    • Worked across four products on different React versions without forcing premature consolidation — pragmatic over ideological.
    Role
    • Collaborated with product owners, backend engineers, designers and QA across four parallel products.
    • Owned ESLint configuration overhaul end-to-end.
    • Pitched and led a Component Library proposal — research, leadership pitch, design-team alignment, first demo components.
    • Conducted regular code reviews and contributed to frontend best practices.
    • Shipped new pages and frontend services to expand product functionality.
    • React
    • Redux
    • RTK Query
    • TypeScript
    • ESLint
    • Microfrontends

  3. Monterosa

    Jan 2019 — Sep 2023

    Front-end Engineer

    Monterosa builds live audience engagement products for sports and media — interactive polls, predictions and live events at broadcast scale. Worked on the core real-time engagement platform with a legacy Ember.js codebase and an evolving design system. The team needed both modernisation (Ember → React) and a unified UI direction. Joined the team from Minsk in January 2019; relocated to Krakow in March 2022 and continued on the same team with the same scope and delivery cadence.

    Outcome

    • Fully rewrote the design system to the new visual language; improved component file structure and accelerated project build.
    • Delivered 20% performance gain on the legacy Ember.js codebase through targeted optimisation and refactoring.
    • Achieved 80-85%+ unit test coverage on the new React.js modules.
    • 4+ year tenure on the same team — endorsed by the CTO and Engineering Lead as a high-trust contributor.
    Role
    • Owned the design-system rewrite to the new visual language.
    • Refactored the legacy Ember.js codebase for performance and maintainability.
    • Built and integrated React.js modules during progressive migration.
    • Wrote unit tests for new React modules and conducted code reviews.
    • Worked across Ember.js, React.js, TypeScript, SCSS, Handlebars, CoffeeScript and Zustand on the same product.
    • Ember.js
    • React
    • TypeScript
    • JavaScript
    • CoffeeScript
    • SCSS
    • Handlebars
    • Zustand
    • Jest
    • React Testing Library

  4. Belitsoft

    Aug 2014 — Dec 2018

    Front-end Developer

    Long-term and short-term frontend work for CMS-based platforms and reusable component libraries — including the Bossrevolution and WebMD platforms and the Lundberg Design site.

    Outcome

    • Played a key role in the Bossrevolution project, improving user experience.
    • Trained and supervised junior colleagues.
    • Contributed to WebMD and Lundberg Design.
    Role
    • Developed maintainable, cross-browser web applications.
    • Created reusable components for faster integration of similar features.
    • Built complex animations and added test coverage.
    • Developed Drupal-based components, admin panel parts, modules, and CKEditor 4.x plugin integrations.
    • HTML
    • CSS
    • JavaScript
    • Drupal
    • CKEditor API
    • Animations
    • Testing

  5. Belitsoft · Startup Labs · EPAM

    2011 — 2014

    Earlier Career

    Three years of foundational frontend work across three studios. Built cross-browser web applications and reusable component libraries (Belitsoft 2011-2013, with the Fishpond.com.au Australian online store client engagement). Supported and enhanced commercial e-commerce frontends (Startup Labs 2012-2013), and shipped corporate sites, advertising microsites and email templates (EPAM Systems 2013-2014). This is the foundation the senior career since 2014 was built on.

    Outcome

    • Shipped reusable component sets that accelerated delivery across multiple client projects.
    • Supported the Fishpond.com.au online store as a frontend contributor.
    • Built cross-browser corporate and advertising sites and email templates at EPAM.
    • HTML
    • CSS
    • JavaScript
    • jQuery

03 / Leadership

Leadership & Engineering Impact

StoneX Group Inc.

In flight

Building a company-wide frontend community

Context
Frontend engineers distributed across 4+ technical teams in multiple offices and countries. Horizontal communication between teams was limited; duplicate work and inconsistent review standards were creeping in.
Action
Currently organising a company-wide frontend community spanning all technical teams and locations — to share patterns, align review standards, and create a shared space for frontend engineers across the entire organisation.
Outcome
In flight.

Synder

Delivered

Pitching and shipping a Component Library

Context
Four microfrontend products on different React versions and no shared UI primitives. Every team was rebuilding the same components from scratch.
Action
Scoped a Component Library proposal end-to-end: research, pitch to leadership, design-team alignment, first demo components.
Outcome
Proposal accepted as a multi-quarter initiative. Working channel between frontend and design established. First demo components delivered against the accepted spec.

Monterosa

Delivered

Rewriting the design system

Context
Legacy Ember.js platform with an inconsistent UI and a slow build. Needed both visual consolidation and structural cleanup.
Action
Owned the design-system rewrite to the new visual language, restructured the component file layout, and accelerated build time — in parallel with progressive React migration.
Outcome
Full design-system rewrite shipped. 20% performance gain on the legacy codebase through targeted refactoring. 80-85%+ unit test coverage on the new React modules.

05 / Principles

How I Build Software

01 / Principle

Refactor before you rewrite

Large rewrites are political projects, not engineering ones. Show the code can be improved incrementally first. At Monterosa, refactoring the legacy Ember.js codebase delivered a 20% performance gain — more than any first-year rewrite would have promised.

02 / Principle

Code review is mentorship, not gatekeeping

Replace "fix this" with "what trade-off did you weigh here?" That's the difference between reviewing for code quality and reviewing for engineer growth. On a long enough timeline, the second matters more. After 8 years at IT Academy, I stopped distinguishing review from teaching.

03 / Principle

A reusable component is an architecture decision, not a tooling one

Storybook doesn't solve a design system — the contract between frontend, design and product does. Storybook documents the decision you already made. At Synder I pitched a custom UI kit not as a set of components, but as a way to lock in that contract.

04 / Principle

Migration without a working legacy is fantasy

Every migration is two parallel stories: how we build the new thing, and how we keep the old one alive. At StoneX the legacy production system cannot break for a single day while migration to React / Next.js is running. Forget the second story and it returns as incidents.

06 / Teaching

Teaching & Mentoring

500+

Students trained

Apr 2017 — Jul 2025

IT-Academy.by

Trainer of Front-end Development Courses

Conducted frontend development courses, mentored students, and supported a learning community focused on HTML, CSS, JavaScript, and web application development.

  • Trained and mentored over 500 students.
  • Helped many students secure positions in big tech companies.
  • Received excellent feedback and testimonials for teaching and mentoring quality.

Courses

  • Web Development with HTML, CSS, and JavaScript
  • Web Application Development with JavaScript
View courseRead reviews

ADPList

Book a Mentoring Session

Open to mentoring sessions on frontend architecture, career progression, technical leadership, and React/Next.js. Booking via ADPList.

Book a Mentoring Session

Topics

  • Frontend Architecture
  • React & Next.js
  • Career Growth
  • Interview Preparation
  • Technical Leadership
  • Code Reviews
  • System Design
  • Developer Experience

07 / Testimonials

What People Say

Yuri is an experienced and knowledgeable client side developer with a range of skills across JavaScript, Ember.js and React.js, and an expert in HTML and CSS. He's been a very valuable member of our team. He takes initiative, strives to come up with the best possible solution, and actively communicates with other team members.

Igor Loboda

CTO @ Monterosa

Direct manager
I've been fortunate to have Yuri in my team for over four years. One of Yuri's most noteworthy achievements has been the complete transformation of our platform's UI — he turned complex designs into code with impressive precision, contributing massively to the design and user experience of our platform. His dedication is commendable; he regularly participates in our processes and is always willing to lend a hand where needed.

Egor Lynko

Engineering Lead @ Monterosa

Direct manager · 4+ years
Yuri has a deep understanding of React, including Redux, React Router, and Hooks. His ability to create efficient, scalable, and user-friendly web applications is remarkable. An excellent problem solver, approaching challenges with a logical mindset — and a great team player who can communicate complex technical concepts clearly to both technical and non-technical stakeholders.

Anhelina Mahidava

Senior Full-Stack Engineer @ Synder

Direct manager
I had the pleasure of working with Yuri when he was setting standards for frontend development at our company. He has a great ability to convey complex ideas in an understandable way and has been very approachable whenever I needed assistance. Yuri provided valuable guidance on pathways for growth in frontend development, which has been instrumental in my own professional development.

Uladzislau Karotki

Organic Growth Manager @ Synder

Cross-functional partner
I was extremely impressed by Yuri's excellent knowledge of programming materials and dedication to teaching. He easily explained complex concepts, making them accessible to all students, and emphasised not only theory but also practical application. His holistic approach — programming, career information, industry context — prepared me for a successful career in development.

Yury Butskevich

Frontend Developer

Mentee at IT Academy

More recommendations available on LinkedIn.

08 / Skills

Skills & Expertise

Core Expertise

  • React.js
  • Next.js
  • TypeScript
  • Tailwind CSS
  • Storybook
  • Redux Toolkit
  • Zustand
  • Vitest
  • Webpack
  • React Testing Library
  • Node.js

Architecture & Engineering

  • Frontend Architecture
  • Design Systems
  • Developer Experience
  • Performance Optimization
  • Scalable UI Systems
  • Accessibility
  • Build Tooling
  • Legacy Modernization
  • CI/CD

Platforms & Domains

  • Vercel
  • Supabase
  • Firebase
  • Sitecore CMS
  • Drupal
  • Microfrontends
  • FinTech
  • Real-time Applications
Previously worked with
  • Ember.js
  • CoffeeScript
  • jQuery
  • Handlebars
  • Bootstrap
  • Chakra UI
  • SCSS
  • PostCSS
  • Vite
  • Parcel
  • EsBuild
  • MongoDB
Languages

Russian — NativeEnglish — B2+Polish — B1+

09 / Certifications

Certifications

Mar 2026 — Mar 2027

Secure SDLC

SecureFlag

  • Software Development Life Cycle (SDLC)
View credential

Apr 2025 — Apr 2026

OWASP Top 10:2021 in NodeJS with TypeScript

SecureFlag

  • Web Application Security Assessment
  • TypeScript
  • Node.js
View credential

10 / Education

Education

  • 2002 — 2007

    Belarusian State University of Informatics and Radioelectronics

    Faculty of Information Technologies and Management

    Artificial Intelligence

    Five-year specialist degree (graduate) in Artificial Intelligence.

  • 2008 — 2010

    Belarusian National Technical University

    Institute of Improvement of Professional Skills and Staff Retraining

    Web Design and Computer Graphics

    Professional retraining programme in Web Design and Computer Graphics.

11 / Contact

Get in touch

Feel free to contact me for frontend engineering roles, mentoring, collaboration, or professional opportunities.