Hire a technical lead who can still do the hard engineering.
I help teams make sound technical decisions and turn them into production software. My strongest lanes are Node.js performance, data visualization, product-funnel optimization, and security research. I lead from architecture through delivery and work directly in the code when that is where the constraint lives. Matching engines, ZK proof systems, and lattice cryptanalysis show how deep that work can go.
Trusted By
What I Build
Technical Leadership & Delivery
I turn product goals into architecture, delivery plans, and working software. I can lead the team, make the hard calls, and stay close enough to the code to remove the real blockers.
Node.js Performance & Architecture
Node.js and NestJS backends, WebSocket systems, queues, caching, database access, and production bottlenecks. I trace the constraint before changing the stack.
Data Visualization & Product Funnels
Custom D3 visualizations, real-time dashboards, and product funnels measured from first visit to conversion. I connect instrumentation, interface decisions, and business outcomes.
Security Research & Applied Cryptography
Protocol review, security-sensitive code, ZK circuits, and cryptographic research tooling. I document the invariant, reproduce the failure safely, and report findings responsibly.
How I Work
Roles
Technical Lead, Staff Engineer, Senior IC, or Frontend/Backend Architect. I align product and engineering, set the technical direction, and help the team ship.
Engagement
Contract (3–12 months) or full-time. I take on 1–2 engagements at a time to give each one full attention.
Stack
Node.js, NestJS, TypeScript, React, Next.js, D3, PostgreSQL, Redis, queues, WebSockets, and cloud infrastructure. Security research and Rust expand the range; they do not replace the stack that best fits the product.
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, Staff Engineer, Senior IC, and Frontend or Backend Architect roles. He has led up to 15 engineers across 3 time zones and remains hands-on with architecture, code, performance work, and incident-level debugging.
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?
Products that need technical direction and difficult implementation work at the same time: Node.js performance, real-time platforms, custom data visualization, measurable product funnels, and security-sensitive systems. Rust and cryptographic tooling are additional specialties, not the center of every engagement.
What is his track record?
18 years shipping production software across 9 companies. Evidence includes leading 15 engineers, a matching engine processing 4000+ orders per second, a D3 platform processing millions of data points, and critical Circom vulnerability findings.
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