Вадим

Vadym Melnychenko
Senior Frontend Engineer | React, Next.js, TypeScript, Node.js
Castel San Giovanni (Piacenza), Italy | Remote preferred | English C1 | Italian A2
Authorized to work in Italy, no sponsorship required
[open contact info](look above in the "contact info" section) | [open contact info](look above in the "contact info" section) | [open contact info](look above in the "contact info" section) | github.com/melnicenkovadik

PROFESSIONAL SUMMARY
Senior Frontend Engineer with 9+ years of commercial experience, specializing in React, Next.js and TypeScript; 5+ years
with Node.js.
Experience includes fintech customer applications and backoffice workflows, Web3 interfaces and LLM-powered legal
tooling. Led a team of 6 developers; ran code reviews and technical interviews.
Founder of Persolingua, a React Native / Expo app and Next.js platform with a NestJS backend. Based in Italy; English C1.
CORE SKILLS
Frontend: React, Next.js (SSR / App Router, code splitting, lazy loading), TypeScript, JavaScript (ES6+), TanStack Query
(React Query), Zustand, Redux Toolkit, MobX, Recoil, GraphQL (Apollo), RESTful APIs, WebSockets, Zod (schema
validation), RxJS, Microfrontends
Mobile: React Native / Expo (Expo Router, EAS builds)
Backend: Node.js, NestJS, Fastify, Redis, Inngest, PostgreSQL, MongoDB
Payments & analytics: Stripe, RevenueCat, GA4 / Google Tag Manager
Design systems / UI: Tailwind CSS, headless component libraries (Radix UI, shadcn/ui), Storybook, Material UI, Chakra UI,
styled-components, SCSS, CSS Modules, Figma, accessibility (a11y)
Build & architecture: Vite, Webpack, Nx / Turborepo monorepos, Atomic Design, design patterns, modular and scalable
frontend architecture
Testing: Vitest, Jest, React Testing Library, Cypress, Playwright (E2E), unit / integration / E2E test suites
CI/CD, cloud & observability: GitHub Actions, GitLab CI, Docker, AWS, Vercel, Sentry (error monitoring)
Performance: Web Vitals, Lighthouse, code splitting, lazy loading, caching (CDN, memoization)
AI & LLM: OpenAI API, Claude API, LangChain, RAG pipelines, prompt engineering, vector databases (Pinecone, Weaviate)
Blockchain / Web3: ethers.js, web3.js, WAGMI, Hardhat
Also: Agile / Scrum
EXPERIENCE
Persolingua (own product)
Founder / Full-Stack Engineer
Jul 2026 - Present
• Built the React Native / Expo iOS and Android app (Expo Router, Reanimated, EAS builds, Sentry, RevenueCat in-app
purchases, Better Auth with Sign in with Apple) with ~1,580 tests; distributed through TestFlight and Google Play internal
testing.
• Developed the Next.js + Drizzle web platform and the NestJS backend, including RevenueCat webhooks, entitlement sync
and Inngest background jobs.
• Owned the web-to-app funnel end to end: Next.js landing with onboarding, Lemon Squeezy web checkout (including gift
courses), then the Expo app, with RevenueCat entitlements tied to the platform user id and GA4 on the landing.

Trustyfy | Fintech / payments (crypto banking cards)
Senior Software Engineer - Frontend
May 2025 - Present
• Architected and built the customer-facing web application end-to-end in React, Next.js, and TypeScript: onboarding flows,
card management, transaction history, and real-time balance tracking over REST and WebSocket APIs, with
Zod-validated forms and Sentry error monitoring in production.
• Built the internal backoffice platform with role-based access control, compliance dashboards, transaction monitoring, and
multi-step approval workflows for financial operations.
• Designed a shared, accessible design system and modular frontend architecture used across both applications, enforcing
coding standards through code reviews and shortening feature delivery.
• Led frontend work and code reviews across the customer-facing app and the internal backoffice.
ZeuZ (contract via Upstaff) | Crypto trading platform
Full Stack Engineer (Contract)
Dec 2024 - Jul 2025
• Sole developer: built a fully functional crypto trading platform with multi-account support, cross and isolated margin
trading, and detailed account statistics.

• Integrated Web3 wallets (MetaMask, Trust Wallet) for secure, private trading without traditional exchange onboarding.
• Designed and user-tested the trading UX end-to-end.
Harvey (contract via Upstaff) | Legal AI
Software Engineer (Contract)
Aug 2024 - Apr 2025
• Built UI for AI-powered legal tools: document-analysis workflows and LLM-driven chat interfaces over complex legal data.
• Integrated large language model capabilities into the product frontend, working with AI and backend teams to ship
responsive, real-time AI-assisted features.
• Contributed to the platform's design system and component library, improving development velocity and UX consistency
across product surfaces.

Optimism Foundation (contract via Upstaff) | Blockchain project (under NDA): secure crypto wallet interfaces and DeFi
Senior Frontend Developer (Contract)
Jul 2024 - Nov 2024
• Implemented decentralized authentication, encryption, and token integration with backend and security teams.
• Optimized UI components for scalability and speed in a crypto environment.
Prof-IT Blockchain
Frontend Team Lead / Full-Stack Web3 Developer
Jan 2023 - Jul 2024
• Led a team of 6 developers building a secure crypto wallet with zero security breaches; improved page load times ~25%
through Next.js performance optimization (code splitting, lazy loading, caching).
• Conducted technical interviews for the frontend team as its lead.
• Delivered Chrome extensions that strengthened blockchain integration and increased user adoption.
• Established code-review processes and weekly knowledge-sharing sessions; sole developer on the Patex ecosystem
(reusable components, Jest / Cypress test suite, multiple feature launches that drove revenue growth).

Coinbase (contract via Upstaff)
Senior React Developer (Contract)
Mar 2022 - Jan 2023
• Integrated advanced analytics and real-time data visualizations into internal tooling, reducing monitoring response times
~20%.
• Optimized Redux state management, reducing load times; built content-management tooling that cut administrative
workload.

Nimbus Platform
Frontend Developer
Feb 2021 - Mar 2022
• Delivered optimized GraphQL APIs in a Next.js codebase with teams across Europe and North America, cutting data-fetch
times ~30%.
• Wrote unit tests, refactored components, and improved documentation and onboarding.
INC4 | Blockchain development
Frontend Developer
Jan 2017 - Jan 2021
• Led blockchain application development for Ambrosus, contributing to successful ICOs and platform launches.
• Modernized legacy React applications, reducing technical debt; built responsive landing pages that raised engagement
and conversion.
• Mentored junior and mid-level developers through code reviews and weekly knowledge-sharing, reducing onboarding time
~40%.

KEY ACHIEVEMENTS
• Built a fintech / payments platform from scratch (Trustyfy): customer-facing app and backoffice, one shared design
system.
• Integrated LLM capabilities into a production legal-tech platform (Harvey) used by 1000+ enterprise customers.
• Shipped crypto wallets and a trading platform with zero security breaches across multiple Web3 products.
• Built and maintained reusable component libraries and design systems (Storybook + Figma), improving development
efficiency ~30%.
• Set up automated CI/CD pipelines (GitHub Actions / GitLab CI) and unit / integration / E2E test suites, accelerating release
cycles.
EDUCATION
Master's degree, Computer Systems Analysis
National University of Life and Environmental Sciences of Ukraine
• Relevant coursework: Software Engineering, Data Structures, Algorithms, Database Systems
LANGUAGES
Ukrainian (native) | Russian (fluent) | English (C1, advanced) | Italian (A2, basic)