Oleksii Vasylenko - Rust & Full-Stack Engineer | Workflow Orchestration, Matching Engines, ZK Proofs, Distributed Systems
Profile
- Production Systems
- Up to 15 Engineers
- 4000+ ops/sec
- Rust to React
Why Hire Me
Mission-Critical Systems, Delivered
Solo-built a workflow orchestration engine in Rust at 2,400+ instances/sec — 7 crates, 3 SDKs, CLI, cloud dashboard, 200+ integrations, every line mine. Plus a matching engine at 4000+ orders/sec, a ZK-SNARK wallet, and a cross-chain messaging protocol. Four domains, all production, all shipped.
Rust to React, No Gaps
Rust engine with PostgreSQL, Go/Python/Node SDKs, WASM pipelines, Solidity smart contracts, React frontends, D3 visualizations, cloud dashboards, DevOps pipelines. One person, zero handoff delays.
18 Years of Shipping
From Singapore fintech to remote blockchain startups — I’ve delivered under every condition. PropertyGuru, Panther Protocol, Mailchain, Bitsten. The work speaks.
Hard problems don’t get easier with time. They get more expensive.
Send me the problemSkills & Technologies
Rust & Systems Programming
Rust · Tokio · Axum · Tonic (gRPC) · SQLx · Wasmtime · WebAssembly · Serde · Systems Architecture · Durable Execution · Message Queues · NATS · jemalloc
Backend Development
Node.js · Express · NestJS · REST APIs · GraphQL · WebSockets · RabbitMQ · API Design · Authentication · Authorization
Blockchain & Cryptography
Solidity · Smart Contracts · Ethereum · Solana · zk-SNARKs · zk-STARKs · Circom · Elliptic Curve Cryptography · Web3.js · Ethers
Frontend Development
React · Next.js · TypeScript · JavaScript (ES6+) · Tailwind CSS · Redux · React Query · Vite · Webpack · Micro Frontends · Core Web Vitals
Data Management
PostgreSQL · MySQL · MongoDB · Redis · KeyDB · 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 · Prometheus
Data Visualization
D3.js · Charting Libraries · Data Storytelling · Interactive Dashboards · Real-Time Data
Deep Dives
Architecture decisions, production lessons, and the thinking behind the systems I have built.
Experience
Full-Stack Developer at Bitsten exchange
- 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
Web3 Developer at Panther Protocol
- 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
Web3 Developer at Mailchain
- 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
Frontend Architect at PropertyGuru
- 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
Frontend Architect at ZuZu Hotels
- 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
Rust Developer at Kobvel Software Consulting
- Developed Rust smart contracts for Solana's Metaplex NFT marketplace with on-chain program architecture
- Implemented Rust-to-WebAssembly compilation pipeline for browser-based blockchain interactions, optimizing binary size under 200KB
- Built client-side cryptographic operations in Rust/WASM — key derivation, transaction signing, balance queries executing in-browser without server round-trips
Rust · WebAssembly · Solana · React · Node.js · Web3
Senior Full-Stack Developer at Xen Technologies
- Implemented ERC-20 compliant smart contracts with KYC-gated transfers for tokenized investment funds
- Built Rust-based tooling for blockchain transaction processing and verification
- Integrated third-party KYC/AML APIs for automated identity verification workflows
React · Webpack · Node.js · Solidity · Rust · TypeScript
Head of Product Development at Data Laboratories
- 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
Full-Stack Developer at Lohika
- 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
The pattern is the same across every role — hard problem in, shipped system out.
Send me yoursSide Projects
A crowdsourced travel scam database built by travelers for travelers. Features a searchable collection of 134+ real scam reports worldwide, a destination scam checker, and a reporting system. Covers everything from taxi fraud and fake police to AI voice-clone kidnapping schemes — helping tourists stay informed before and during trips.
Next.js · TypeScript · TailwindCSS
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
AI-powered spaced repetition platform for language learners. Uses the FSRS algorithm for 90% long-term retention, generates flashcards from any text via AI, and exposes an Anki-compatible API. Supports 31 languages, offline study, and cross-platform use (iOS + web). Solo-built from the ground up.
Next.js · React Native · TypeScript · PostgreSQL · FSRS · AI/LLM
AI-powered preparation platform for CELPE-BRAS, Brazil's official Portuguese proficiency exam. 411+ practice tasks across 13 text genres, AI grading on all 5 official criteria, timed mock exams, and voice-based speaking practice. Solo-built to replace $30–80/hour tutoring with unlimited AI feedback at a fraction of the cost.
Next.js · TypeScript · AI/LLM · Speech Recognition · PostgreSQL
AI-powered reading-based language learning. Users photograph book pages in any language and get sentence-by-sentence translations, grammar explanations, vocabulary breakdowns, and auto-generated exercises. Supports 12+ languages with Anki flashcard export. Solo-built to let learners read real books from day one.
Next.js · TypeScript · OCR · AI/LLM · 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
Featured Open Source
Source-available durable workflow orchestration engine built in Rust — solo project, every line of code written by me. Designed and shipped the full stack alone: the core engine with crash recovery and hot migration, typed SDKs in three languages, a CLI, a cloud dashboard, and 200+ integrations. Handles email campaigns, billing retries, and AI agent workflows with automatic scheduling, rate limiting, and state durability. Extended with orch8-solana for durable Solana transactions — submitted to the Colosseum Solana Hackathon 2026.
Rust · Solana · PostgreSQL · Docker · Helm · REST API · SSE · NATS · WASM · gRPC · Node.js · Python · Go · AES-256-GCM
Open Source
Curated list of resources for learning and building with Zero-Knowledge Proofs — foundational concepts, research papers, proof systems (SNARKs, STARKs, folding schemes), libraries, tutorials, and real-world applications.
ZKP · SNARKs · STARKs · Cryptography
Curated compilation of resources for Solana development — program architecture, client SDKs, DeFi protocols, NFT tooling, validator operations, and ecosystem references.
Solana · Rust · Anchor · Web3
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
Education
Bachelor of Computer EngineeringWith Honors
Sevastopol National Technical University
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
Communities
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.