# Oleksii Vasylenko — Hands-on Technical Lead and Systems Engineer ## About Oleksii Vasylenko is a hands-on technical lead with 18+ years shipping production systems across fintech, crypto, travel, and enterprise software. His primary specialties are Node.js performance and architecture, custom D3 data visualization, product-funnel optimization, and security research. He has led teams of up to 15 engineers across 3 time zones and works from technical direction through implementation. Rust, systems programming, and cryptographic tooling are growing specialties and active research interests rather than his primary job title. His technical depth includes a matching engine processing 4000+ orders/sec with sub-millisecond latency, production zero-knowledge proof systems and Circom circuit security work, and current lattice cryptanalysis research covering LLL, BKZ, sieving, hidden-number attacks, and post-quantum security tooling. ## Currently Available for remote technical leadership, architecture, performance optimization, and senior individual contributor roles. Open to contract and full-time. Hire page: https://www.ovasylenko.com/hire ## Primary Positioning - Technical Lead — product and engineering alignment, architecture, delivery, and hands-on implementation - Node.js Optimization — Node.js and NestJS services, WebSockets, queues, caching, database access, and performance diagnosis - Data Visualization — 7 years of D3 across 3 companies, including real-time systems with millions of data points - Funnel Optimization — instrumentation, conversion-path diagnosis, frontend performance, and experiments tied to business outcomes - Security Research — protocol review, responsible disclosure, ZK circuit security, threshold-signing systems, and cryptanalytic tooling - Rust — an emerging specialty used for systems and research work, not the primary professional identity - Deep-system evidence — matching engines, ZK proof systems, and lattice cryptanalysis ## Deep Dives — Architecture & Production Lessons These pages go beyond the resume bullet points. Each covers the architecture decisions, failure modes, and production lessons behind a specific domain. - ZK-SNARK Development — From Circuits to Production Wallets: https://www.ovasylenko.com/expertise/zk-snark Circuit-level security audits, UTXO wallet engines, and browser-optimized proof generation at Panther Protocol. - Matching Engine Technology & Architecture: https://www.ovasylenko.com/expertise/matching-engines How to build a deterministic order book, operate it safely, and recover it after failure, with production lessons from a live exchange processing 4000+ orders/sec. - Micro Frontends in React — Production Architecture: https://www.ovasylenko.com/expertise/micro-frontends Module Federation, domain boundaries, routing, shared state, deployment, observability, and a production migration for 4 product teams. ## Supporting Engineering Guides - Order Book Data Structures for a Matching Engine: https://www.ovasylenko.com/blog/order-book-data-structures-matching-engine Price-level indexes, FIFO queues, cancellation maps, fixed-point arithmetic, memory layout, partitioning, and recovery invariants. - Micro Frontends vs Modular Monolith: https://www.ovasylenko.com/blog/micro-frontends-vs-modular-monolith A decision framework for team autonomy, deployment contention, runtime cost, failure isolation, and migration. - Rust and WebAssembly — Native Performance in the Browser: https://www.ovasylenko.com/expertise/rust-webassembly Rust-to-WASM compilation for blockchain clients, cryptographic operations, and Solana smart contracts. - Smart Contract Development — Solidity to Solana: https://www.ovasylenko.com/expertise/smart-contracts Production smart contracts across Ethereum and Solana — ERC-20 tokens, NFT marketplace programs, and ZK privacy layers. - Real-Time Systems — WebSockets, Message Queues, and Live Data: https://www.ovasylenko.com/expertise/real-time-systems Backpressure handling, snapshot-plus-diff patterns, and streaming pipelines for trading platforms and enterprise dashboards. - D3.js and Data Visualization — Making Data Tell Stories: https://www.ovasylenko.com/expertise/d3-data-visualization 7 years of D3 across 3 companies. Real-time dashboards, flight route maps, and executive analytics. - Cross-Chain Protocols — Connecting Blockchains: https://www.ovasylenko.com/expertise/cross-chain-protocols Protocol abstraction layers, wallet adapter patterns, and TypeScript SDKs — Ethereum to Near to ENS in one interface. - Frontend Architecture for Financial Systems — When Every Frame Counts: https://www.ovasylenko.com/expertise/fintech-frontend-architecture 60fps order books, offline-capable booking systems, and Core Web Vitals optimization for trading and payment UIs. - Database Architecture and Performance — Designing Data Systems That Scale: https://www.ovasylenko.com/expertise/database-architecture Polyglot data architecture — PostgreSQL, MongoDB, Redis, KeyDB — choosing the right database per workload. - Rust for Mission-Critical Systems — Why Rust When Failure Is Not an Option: https://www.ovasylenko.com/expertise/rust-mission-critical Ownership model eliminates data races, use-after-free, and null dereferences before production. Matching engines, workflow orchestrators, and cryptographic pipelines built in Rust. - Durable Workflow Engine Architecture — Beyond Temporal, Snapshot-Based Execution: https://www.ovasylenko.com/expertise/durable-workflow-engines Solo-built a Temporal alternative in Rust. 7-crate workspace, snapshot-based state persistence, O(1) resume, no history replay, no determinism constraints. - Lattice Cryptanalysis — LLL, BKZ, and Sieving in Production Rust: https://www.ovasylenko.com/expertise/lattice-cryptanalysis Solo-built g6k-rs, a 16K-line Rust lattice reduction library: LLL, BKZ 2.0, three sieve algorithms, CVP solvers, Coppersmith, LWE attacks, and ECDSA key recovery from partial nonce leakage. - Post-Quantum Cryptography Tooling — Optimizing the Leading Lattice Sieving Toolkit: https://www.ovasylenko.com/expertise/post-quantum-cryptography-tooling Performance engineering on G6K's C++ sieving engine and a 100× faster Rust spherical code generator with incremental Gram matrix updates for SimHash probe banks. ## Writing - OPAQUE Password Authentication in TypeScript: OPRFs, Envelopes, and 3DH (July 2026): https://www.ovasylenko.com/blog/opaque-password-authentication-typescript Source-level analysis of the OPAQUE augmented PAKE: OPRF password blinding, client credential envelopes, 3DH mutual authentication, session-key derivation, fake records, and production deployment risks. - How I Made G6K's Spherical Code Generator 100× Faster (June 2026): https://www.ovasylenko.com/blog/g6k-spherical-code-generator-100x-faster Incremental Gram matrix updates turn O(N·n) per-swap cost into O(N); Rust rewrite of the leading lattice sieving toolkit's code generator with byte-identical output. - How to Become a Protocol Developer: A Comprehensive Guide (December 2024, Medium): https://medium.com/@oleksii.vasylenko/how-to-become-a-protocol-developer-a-comprehensive-guide-42cad52a2f77 ## Work Experience - Bitsten exchange (June 2024 - Feb 2025): Full-Stack Developer. Architected matching engine processing 4000+ orders/sec with sub-millisecond latency. Built WebSocket-based trading system for thousands of concurrent users. - Panther Protocol (June 2023 - June 2024): Web3 Developer. Built zk-SNARK wallet engine supporting multiple blockchains. Identified and resolved critical vulnerabilities in Circom circuits. - Mailchain (March 2022 - June 2023): Web3 Developer. Integrated Ethereum, ENS, and Near for wallet-to-wallet messaging. Created TypeScript SDKs for third-party developers. - PropertyGuru (April 2020 - March 2022): Frontend Architect. Led monolith to micro frontend migration for 4 teams. Engineered unified payment service adopted across all product teams. - ZuZu Hotels (January 2020 - April 2020): Frontend Architect. Implemented PWA features for offline booking. Singapore. - Kobvel Software Consulting (November 2019 - January 2020): Rust Developer. Developed smart contracts for Solana's Metaplex NFT marketplace. Implemented Rust to WebAssembly compilation. - Xen Technologies (December 2018 - November 2019): Senior Full-Stack Developer. KYC/AML integrations and ERC-20 smart contracts. Singapore. - Data Laboratories (August 2015 - December 2018): Head of Product Development. Led team of 15 engineers across 3 time zones. Architected D3-based data visualization platform. Singapore. - Lohika (May 2011 - August 2015): Full-Stack Developer. Built real-time flight data visualization for travel agents. Integrated Amadeus GDS. Odessa, Ukraine. ## Personal Projects - scam.travel (https://scam.travel) — Crowdsourced travel scam database with 134+ real scam reports worldwide - Lattices.io (https://lattices.io) — Interactive educational reference for post-quantum cryptography with 3D lattice visualizations - TRounds (https://trounds.com) — Tabata/HIIT interval timer app with Spotify integration - Trading Statement (https://tradingstatement.io) — Fintech analytics platform for traders - Skillcrucial.com (https://skillcrucial.com) — Online coding school, 3,000+ users - Mynft.is (https://mynft.is) — NFT portfolio dashboard ## Teaching & Community - Skillcrucial: Founded and mentored 3,000+ developers through JavaScript and React curriculum - ZK-monk (https://www.zkmonk.org): Lecturer on Elliptic Curve Cryptography and zero-knowledge proof mathematics ## Contact - Email: hello@ovasylenko.com - Website: https://ovasylenko.com - GitHub: https://github.com/ovasylenko - Twitter: https://twitter.com/_alphaGeek - Medium: https://medium.com/@oleksii.vasylenko - StackOverflow: https://stackoverflow.com/users/3815605/rocktheworld ## Core Skills - React, Next.js, TypeScript, Node.js - Rust, WebAssembly, Systems Programming - Zero-Knowledge Proofs, Cryptography, Blockchain - Software Architecture, Distributed Systems - D3.js, Data Visualization, Real-Time Systems - PostgreSQL, AWS, Docker, Kubernetes ## Education - Bachelor of Computer Engineering (With Honors) — Sevastopol National Technical University (2006-2011) - Focus: Systems programming, distributed computing, cryptography ## Portfolio View full portfolio and work experience at https://ovasylenko.com