I build the systems your business can't afford to get wrong.
18 years shipping production infrastructure across fintech, crypto, and enterprise. From React frontends to Rust backends, Solidity smart contracts to D3 visualization platforms. One person, zero handoff delays, full ownership from architecture to deployment.
Trusted By
What I Build
Complex System Architecture
Matching engines, trading platforms, real-time data pipelines, message queue systems. The kind of infrastructure where a bug costs real money.
Blockchain & Cryptography
ZK-SNARK circuits, smart contracts on Ethereum and Solana, cross-chain protocol layers, Rust-to-WASM pipelines. Privacy-preserving systems that actually ship.
Frontend at Scale
Micro frontend migrations, 60fps trading UIs, D3 visualization platforms, PWAs with offline capability. For teams that have outgrown their monolith.
How I Work
Roles
Technical Lead, Senior IC, Staff Engineer, Frontend/Backend Architect. I am comfortable leading teams or going deep as an individual contributor.
Engagement
Contract (3–12 months) or full-time. I take on 1–2 engagements at a time to give each one full attention.
Stack
React, Next.js, TypeScript, Node.js, NestJS, Rust, WebAssembly, Solidity, PostgreSQL, MongoDB, Redis, Docker, AWS, GCP. I pick the right tool for the job, not the one I used last.
Timezone
Based in Brazil (UTC−3). Full overlap with US East Coast. 4–5 hours overlap with Western Europe. Async-first by default.
By the Numbers
Frequently Asked Questions
What roles does Oleksii Vasylenko take on?
Technical Lead, Senior IC, Staff Engineer, and Frontend or Backend Architect roles. He is comfortable leading teams — he has led up to 15 engineers across 3 time zones — or going deep as an individual contributor.
Does Oleksii work on contract or full-time?
Both. Contract engagements typically run 3 to 12 months, and full-time roles are also an option. He takes on 1 to 2 engagements at a time to give each one full attention.
What timezone does Oleksii work in?
He is based in Brazil (UTC-3), which gives full overlap with the US East Coast and 4 to 5 hours of overlap with Western Europe. He works async-first by default.
What kind of projects is Oleksii best suited for?
Systems where a bug costs real money: matching engines, trading platforms, and real-time data pipelines; blockchain and cryptography work including ZK-SNARK circuits, smart contracts on Ethereum and Solana, and cross-chain protocol layers; and frontend at scale — micro frontend migrations, 60fps trading UIs, and D3 visualization platforms.
What is his track record?
18 years shipping production infrastructure across 9 companies, including Bitsten exchange, Panther Protocol, Mailchain, PropertyGuru, Xen Technologies, Data Laboratories, and Lohika. Highlights include a matching engine processing 4000+ orders per second and leading teams of up to 15 engineers.
How do I start a conversation?
Email hello@ovasylenko.com and describe what you are building and what is blocking you. He will tell you honestly whether he is the right person for it.
Hard problems don't get easier with time. They get more expensive.
Tell me what you are building and what is blocking you. I will tell you honestly whether I am the right person for it.
Start a conversation