Oleksii Vasylenko
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
An eight-state effect ledger, deterministic effect IDs, storage-enforced at-most-once dispatch, and why an ambiguous outcome should block a retry rather than guess.
Determinism constraints, resume cost, versioning, payload limits, and debuggability compared honestly — including what each model gives up to the other.
The SKIP LOCKED claim query, partial indexes, per-tenant fairness, the window-function restriction that broke the first version, lease heartbeats, and where this design stops scaling.
Epoch fencing, capability-checked capsules, effect receipts that survive relocation, hash-chained provenance, and federation envelopes that fail closed.
Per-tenant circuit breakers with persisted Open state, fair claim caps, tenant-scoped coordination, and epoch-fenced storage routing with no default backend.
Nearly every requirement here exists because production made it necessary: trading rules, consistency, ledger integrity, throughput, recovery, operations, and launch acceptance.
The Redis lock that could delete someone else's lock, the queue setting that replaced it, and where parallelism actually pays in a price-time engine.
Matching cells, hash-tag atomic commits, WAITAOF durability, the two kinds of duplicate, outbox delivery, and honest horizontal-scaling evidence.
Four boundaries, four correct answers — plus three results that went the wrong way: a faster datastore that was slower, two cells slower than one, and durability costing 8x.
Encoding FIFO priority into a Redis sorted-set member, plus price levels, cancellation indexes, fixed-point arithmetic, memory layout, and the invariants that actually break.
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.