OleksiiVasylenko
Hands-on Technical Lead. Node.js performance, data visualization, product funnels, and security research — with matching engines, ZK proof systems, and lattice research as evidence of depth.
Best fit: hands-on Technical Lead · performance and product systems · remote UTC−3
Profile
- Production Systems
- Up to 15 Engineers
- 4000+ ops/sec
- Node.js · D3 · Security
Why Hire Me
Direction and Delivery in One Person
I connect product goals to architecture and delivery without disappearing into management. I have led 15 engineers across three time zones, helped four teams deploy independently, and personally built the performance-critical parts when the work demanded it.
Performance, Data, and Conversion
My core range joins Node.js architecture, real-time systems, D3 visualization, frontend performance, and product-funnel analysis. That makes it possible to trace a business problem across the interface, instrumentation, API, queue, cache, and database instead of optimizing one layer in isolation.
Security Is Part of Engineering
I review protocols and security-sensitive code with an engineer's understanding of how systems fail. My work includes critical Circom vulnerability findings, threshold-signing protocol research, responsible disclosure, and cryptographic attack tooling. Rust is an active area of systems research, not a marketing label.
Hard problems don’t get easier with time. They get more expensive.
Send me the problemSelected Impact
Architecture matters when it changes an operating number—not when it makes a diagram look impressive.
4,000+ orders/sec
Bitsten exchange
Constraint
A live exchange needed predictable matching, deeper liquidity, and price updates that stayed accurate under load.
Decision
Architected the matching engine, integrated market-maker APIs, rebuilt OHLCV generation, and added full order-book test coverage.
Outcome
Sub-millisecond matching latency, 3× deeper order books, and real-time market data delivered to thousands of concurrent users.
Weeks → days
PropertyGuru
Constraint
Four product teams shared a frontend monolith. Releases were coupled, slow, and required coordination across team boundaries.
Decision
Split ownership by business domain, introduced Module Federation, and built one payment service with a contract shared by all four teams.
Outcome
Teams deployed independently and the release cycle moved from weeks to days without duplicating payment logic.
2,400+ instances/sec
Orch8
Constraint
Durable automation usually forces application code into replay rules, activity wrappers, and growing event histories.
Decision
Built a Rust engine around snapshot persistence, crash recovery, hot migration, typed SDKs in Node.js, Python, and Go, plus 200+ integrations.
Outcome
Under 3ms per workflow instance, 1.04× degradation at 1,000 runs, and no replay tax in application code.
If one of these constraints looks familiar, send the failure mode—not a polished brief. That is enough to start a useful technical conversation.
Discuss a similar constraintExperience
Security Researcher at Independent Security Research
- Conducted independent security research on Threshold Network / tBTC, reviewing its distributed threshold-signing client (Go) and bridge contracts (Solidity)
- Identified a quorum-synchronization invariant gap in the protocol's post-signing completion path, where signing-done accounting was not bound to the exact attempt's selected signer set — a protocol liveness / safety-margin (griefing) class issue rather than key, signature, or fund compromise
- Reproduced the issue deterministically in an isolated local test harness, limiting live interaction to read-only checks with no state-changing actions on production or public test networks
- Authored an Immunefi-style technical write-up and submitted it through coordinated responsible disclosure
- Ran a tECDSA / hidden-number-problem lattice anomaly scan over public Bitcoin signatures (duplicate-nonce, scalar-range, and nonce-bias triage) as part of the cryptographic review
Go · Solidity · Threshold Signatures (tECDSA) · Bitcoin · Lattice Cryptanalysis · Immunefi
Technical Lead / 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 yoursFeatured 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
Deep Dives
Architecture decisions, production lessons, and the thinking behind the systems I have built.
Side 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
Open Source
High-performance lattice sieving and reduction library in Rust. Implements LLL, deep insertion LLL, BKZ 2.0 with Schnorr-Euchner enumeration and sieve-based SVP oracles (BDGL, BGJ1, HK3), Babai CVP solvers, Coppersmith small-root finding, LWE attack via Kannan embedding, and arbitrary-precision lattices via GMP. Includes multi-threaded and Metal GPU-accelerated sieve variants. 16K+ lines, 215 tests.
Rust · Lattice Cryptography · LLL/BKZ · SIMD · Metal GPU
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
Writing
Price levels, FIFO queues, cancellation indexes, fixed-point arithmetic, memory layout, partitioning, and production invariants for low-latency order books.
A decision framework based on team autonomy, release contention, domain ownership, runtime cost, failure isolation, and platform responsibility.
A source-level study of the OPAQUE augmented PAKE: password blinding, credential envelopes, 3DH session keys, fake records, and the details that decide whether an implementation is safe to deploy.
Incremental Gram matrix updates turn an O(N·n) per-swap cost into O(N). A Rust rewrite of the leading lattice sieving toolkit's code generator — byte-identical output, full n=6..1000 sweep on a laptop.
Blockchain fundamentals, distributed systems, and cryptography — the full path from application developer to protocol engineer.
Skills & Technologies
Technical Leadership & Product
Software Architecture · Technical Direction · Team Leadership · Product Engineering · Delivery Planning · Funnel Optimization · Conversion Instrumentation · Core Web Vitals
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
Security Research
Protocol Review · Responsible Disclosure · ZK Circuit Security · Threshold Signatures · Smart Contract Security · Lattice Cryptanalysis
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.