Senior UI Engineer & Full Stack

SaaS, FinTech, E-commerce, EdTech, AI products, CRM / ERP, Healthcare, Travel, Media, Social, Developer tools, Cybersecurity, Marketplace, Logistics

Let's discuss details

Available for remote B2B contracts globally

Iryna Vynnychenko

Iryna Vynnychenko

Senior UI Engineer & Full Stack Developer

Iryna Vynnychenko, senior UI engineer & full stack developer in Kyiv. React and Next.js for SaaS, MVPs, and Telegram Mini Apps. 8+ years in production, 4,200+ Upwork hours, 100+ launched projects.

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Highlights8+ years4,200+ Upwork hours100% Job Success100+ launched projects

Hire me for

Sites, web apps, Mini Apps, and AI – shipped as a senior engineer, not an agency handoff.

Website development

Marketing sites on Next.js, WordPress, or Webflow – stack from the job, not from a trend.

Web app development

Product UIs on Next.js and React – dashboards, accounts, booking, checkout.

Telegram Mini App development

Mini Apps, payment bots, booking, shops – Next.js inside Telegram.

AI solutions for business

RAG on your data, agents with a human confirm, CRM hooks – ROI, not a demo chatbot.

About

Front-End Heavy Senior UI Engineer: Pixel-Perfect UI, React & Next.js SaaS, AI Products & Telegram Mini Apps.

Pixel-perfect UI is my life’s commitment. I take 100% ownership of the front-end heavy contour in React and Next.js – from Figma to production, streaming UI, and seamless ML/AI integration.

Front-End Heavy Senior UI Engineer. Pixel-Perfect React and Next.js in production.

What I take on

  • 8+ years in production: SaaS, MVPs, Web Apps on React and Next.js (4,200+ Upwork Hours)
  • Senior UI Engineer & Front-End Heavy Partner for ML Engineers: Pixel-Perfect UI, UI/UX to Code, streaming UI, human-in-the-loop validation
  • Solo Developer (No Agency): 100% accountability. Direct communication, remote B2B contracts globally, NDA-ready

Stack

ts iconreact iconangular iconsvelte iconnodejs iconflask iconpostgres icontailwind iconredux icongit iconvercel icondocker iconhtml iconfigma iconjest iconcloudflare icon
js iconnextjs iconvue iconthreejs iconpython iconphp icongraphql iconsass iconvite icongithub iconaws iconplaywright iconcss iconnpm iconwordpress icon

Core Frontend & Architecture

  • TypeScript, JavaScript (ES6+), React, Next.js (App Router, Server Components, Server Actions, API Routes)
  • Angular, Vue.js, Svelte, Alpine.js
  • Tailwind CSS, SCSS, CSS Modules, Styled Components, shadcn/ui
  • Pixel-Perfect UI development, design systems & accessible (a11y) UI kits
  • GSAP, Framer Motion, Lottie, Google Maps API
  • Webflow, WordPress, static generation (SSG / HTML)

AI Integrations & Features

  • Vercel AI SDK
  • Figma-to-Code via MCP
  • Streaming UI (SSE / WebSockets)
  • AI-assisted development & AI-powered internal tools
  • Workflow automation
  • Multimodal AI

AI Automation & Agentic Workflows

  • AI agents & agentic workflow automation
  • Business process automation
  • Human-in-the-loop validation & confirmation UI
  • API orchestration & automated data processing
  • Context engineering & tool / function calling
  • Structured outputs & schema validation
  • Embeddings & vector databases

LLM Integrations

  • OpenAI & Anthropic APIs
  • Prompt engineering
  • Structured outputs & tool/function calling
  • Embeddings & vector databases
  • Context management & token optimization
  • AI agents & multimodal AI

Backend & Databases (Complex Backend)

  • Node.js, Python, Flask, PHP
  • PostgreSQL, Prisma ORM
  • Docker (Containerization)
  • API Integration & Orchestration (REST / GraphQL)

State & Data Visualization

  • React Query / TanStack Query
  • Redux, Zustand, Context API
  • GraphQL & REST APIs (JSON / data parsing)
  • ECharts.js & data visualization

Performance & Architecture

  • SSR / SSG / ISR / CSR
  • Core Web Vitals optimization
  • Bundle size & load-time reduction · code splitting & lazy loading
  • i18n / multilingual architecture
  • SEO & semantic HTML structure
  • Component-based & feature-based architecture · custom hooks

Testing, Tooling & AI Workflows

  • Git / GitHub, CI/CD
  • AWS (S3, CloudFront, Amplify / Serverless)
  • Vercel, VPS servers, Netlify
  • Jest, React Testing Library, Playwright
  • AI-augmented tooling: Claude Code MAX, Gemini, Codex, Cursor IDE

Additional / Earlier Experience

  • Joomla
  • jQuery, Pug (Jade), Bootstrap

Projects(100+)

  • Multi-tenant product systems on Next.js + PostgreSQL/Prisma - isolated data, built to grow from dozens to thousands of users
  • High-traffic delivery: SSR/SSG/ISR, CDN caching (CloudFront / Vercel Edge / VPS), code splitting, Core Web Vitals under load
  • AWS serverless: S3, CloudFront, Amplify - preview vs production isolation, CI/CD, repeatable deploys
  • API backends at scale (Node.js, REST/GraphQL) with TanStack Query - cache, retries, and optimistic UI for live products

Selected public work

massageschool.com.ua

niunkina.com

plowguys.com

franchise.plowguys.com

Client Testimonials

“Iryna turned our Figma design into a live page flawlessly and ahead of schedule.”

Client

Figma to Live Page

Upwork profile

Independent contractor since 2018

Frequently Asked Questions

Answers to common questions about working together

What is your typical project workflow?

For a marketing site we start from the brief or Figma. For product work we start from the domain: business rules, data model, existing APIs. Then architecture, milestones, iterative delivery with daily updates, QA, and deploy. You work with me directly - no middle managers.

Do you work under NDA (Non-Disclosure Agreement)?

Yes, absolutely. I value my clients' security and intellectual property. I am fully ready to sign a standard NDA before we discuss any confidential project details or share source code.

Which technologies do you specialize in?

Frontend: Webflow, WordPress, static sites, GSAP / Lottie / Framer Motion. Fullstack: Next.js - Server Components, Server Actions, API Routes, PostgreSQL / Prisma. TypeScript on the whole path.

How do we get started?

We can schedule a video call or chat via Upwork/Telegram/WhatsApp to discuss your project scope. Once we align on requirements, I can provide a fixed-price estimate or start on an hourly basis.

Do you work with Ukrainian companies as a registered private entrepreneur?

Yes, absolutely. I am officially registered as a private entrepreneur (Group 3) in Ukraine, meaning we can sign an official contract for web development services, issue invoices, and sign acceptance acts.

How do you drive value?

Architecture & MVPs, performance, design systems, full-stack debugging, and AI-powered backend engineering.

  • Architecture & MVPs: Scoping and launching scalable web products from zero to production.
  • Performance: Auditing legacy code, cutting bundle sizes, and maximizing page speed.
  • Design Systems: Building reusable, accessible (a11y) UI kits for complex apps.
  • Full-Stack Debugging: Tracking down and fixing production issues across frontend & backend.
  • AI-Powered Backend & Agentic Engineering (Node, Python, PHP): Applying agentic engineering practices - using Cursor & Claude to handle implementation under clear human guidance and test coverage to deliver secure APIs, backend logic, and automated workflows.

What do you build?

Available for end-to-end development or jumping in at any stage:

  • Marketing sites: Webflow, WordPress, static HTML, landings and corporate sites.
  • Animation and interaction: GSAP, Lottie, Framer Motion.
  • Fullstack Next.js: UI, APIs, PostgreSQL / Prisma in one web app. NDA-ready.

Let's work together

SaaS, MVPs, and product UI on React and Next.js. Scope and timeline on a short call.

Get in touch
Hire me on Upwork

i.vynnychenko@gmail.com