Oleksii Vasylenko - Technical Lead and Full-Stack Developer Portfolio

Frontend Development

React · Next.js · TypeScript · JavaScript (ES6+) · Tailwind CSS · Redux · React Query · Vite · Webpack · Micro Frontends · Responsive Design · Accessibility (a11y) · Core Web Vitals

Backend Development

Node.js · Express · NestJS · REST APIs · GraphQL · WebSockets · Message Queues · API Design · Authentication · Authorization

Data Management

PostgreSQL · MySQL · MongoDB · Redis · Database Design · Query Optimization · Data Modeling · Database Migrations

Cloud & DevOps

AWS · GCP · Docker · Kubernetes · CI/CD Pipelines · Infrastructure as Code · Serverless Architecture · Vercel · GitHub Actions · Terraform

Web3 & Blockchain

Solidity · Smart Contracts · Ethereum · Web3.js · Decentralized Applications (dApps) · Blockchain Protocols · Cryptography · Wallet Integration

Data Visualization

D3.js · Charting Libraries · Data Storytelling · Interactive Dashboards · Real-Time Data

• Architected matching engine processing 4000+ orders/sec with sub-millisecond latency
• Engineered liquidity bots integrating multiple market maker APIs, improving order book depth by 3x
• Redesigned candle engine architecture for accurate OHLCV data generation and real-time charting
• Built WebSocket-based trading system delivering instant price updates to thousands of concurrent users
• Developed automated testing framework achieving full coverage of order book and matching engine logic
• Integrated CoinGecko API for market data aggregation, enabling platform listing

React · Node · TypeScript · Nest · RabbitMQ · KeyDB

• Built zk-SNARK wallet engine supporting multiple blockchains with UTXO-based transaction model
• Implemented end-to-end encryption protocol for secure cross-chain messaging
• Identified and resolved critical vulnerabilities in Circom circuits during security audits
• Integrated zero-knowledge proof system for private transactions while maintaining verifiability

React · Service Workers · zk-STARK · zk-SNARK · Circom · Elliptic Curve Cryptography

• Integrated major blockchains including Ethereum, ENS, and Near for wallet-to-wallet messaging
• Built encryption test suite ensuring secure message delivery across protocols
• Developed Near Mailchain Widget enabling dApps to embed messaging functionality
• Optimized UI performance achieving high Lighthouse scores for Core Web Vitals
• Implemented wallet integrations for MetaMask, WalletConnect, and other popular providers
• Created TypeScript SDKs with comprehensive documentation for third-party developers

React · D3 · Node.js · WebSockets · Ethers · Rollup · Webpack

• Engineered unified payment service adopted across 4 product teams, eliminating duplicate code
• Led monolith → micro frontend migration, enabling 4 teams to deploy independently
• Implemented Webpack Module Federation reducing deployment coupling and release cycle from weeks to days
• Built interactive Tableau dashboards used by executives for real-time business decisions

React · NestJS · D3 · Node.js · Tableau · WebSockets

• Implemented Progressive Web App features for offline booking capability
• Established component-driven development workflow with Storybook documentation
• Optimized bundle size and initial load times using Webpack code splitting

TypeScript · React · Webpack · S3 · PWA · Storybook

• Developed smart contracts for Solana's Metaplex NFT marketplace
• Created frontend interfaces for Solana-based e-commerce platforms
• Implemented Rust to WebAssembly compilation for browser-based blockchain interactions

Rust · WASM · React · Node.js · Web3

• Integrated third-party KYC/AML APIs for identity verification workflows
• Developed responsive web applications for cross-platform compatibility
• Implemented ERC-20 compliant smart contracts for tokenized investment funds

React · Webpack · Node.js · Solidity · Rust · TypeScript

• Led team of 15 engineers across 3 time zones, shipping on tight deadlines
• Architected D3-based data visualization platform processing millions of data points in real time
• Established security protocols adopted as company-wide standard for enterprise clients

React · D3 · WebSockets · .NET Core · CoffeeScript

• Built real-time flight data visualization used by thousands of travel agents daily
• Integrated Amadeus GDS and Google Maps APIs powering end-to-end travel booking flow
• Developed ASP.NET MVC backend services handling high-traffic travel search and booking

ASP.NET MVC · D3.js · Node.js · Angular

An interactive educational reference for mathematical lattices and post-quantum cryptography. Covers lattice theory from first principles through advanced topics including SVP/CVP, LWE, Ring-LWE, SIS, NTRU, ML-KEM (Kyber), ML-DSA (Dilithium), and Fully Homomorphic Encryption — with 3D lattice visualizations and gradually increasing complexity.

Next.js · TypeScript · Three.js · TailwindCSS

A Tabata/HIIT interval timer mobile and web app with customizable workout presets, Spotify integration, workout history tracking, and real-time visual feedback. Built as a cross-platform solution with React Native for mobile and Next.js for web.

React Native · Expo · Next.js · TypeScript · TailwindCSS

Developed tradingstatement.io, a fintech platform that helps traders track and analyze their trading performance, providing detailed insights and analytics for better decision making.

React · Node.js · TypeScript · PostgreSQL · AWS

Founded Skillcrucial.com, an online coding school, where I designed a robust CMS and created distributed systems for efficient task validation. Since its launch, Skillcrucial.com has attracted over 3,000 users, facilitating a community-driven learning platform for aspiring developers.

React · Node.js · MongoDB · Redis · Docker

Developed an NFT dashboard (mynft.is) offering comprehensive data visualization and portfolio management, leveraging OpenSea and Ethereum data.

Next.js · Web3.js · Ethereum · GraphQL · TailwindCSS

Developed JavaScript SDK for Mailchain, a messaging protocol enabling cross-protocol communication. The SDK allows users to send messages to any blockchain address across different protocols, making blockchain communication more accessible and unified.

TypeScript · Node.js · Web3 · Blockchain

Five-year program covering low-level systems programming, computer architecture, networking protocols, and applied mathematics. Thesis focused on optimizing task distribution algorithms in heterogeneous distributed computing environments.

• Graduated with honors — top of class in systems programming and applied mathematics
• Thesis: optimization of load balancing algorithms for distributed computing clusters
• Coursework in cryptography, compiler design, operating systems, and database internals

Skillcrucial

Founded an online coding school that grew to 3,000+ users. Designed the curriculum, built the CMS and distributed task validation system, and personally mentored students through JavaScript and React fundamentals. The platform ran for several years as a community-driven learning environment for career-switching developers.

ZK-monk

Lecturer on Elliptic Curve Cryptography at zkmonk.org. Teaching the mathematical foundations behind zero-knowledge proofs — from finite fields and group theory through pairing-based cryptography — to developers building privacy-preserving protocols.