I'm Andrii Zelenets - a Full-Stack Software Engineer with 13 years of production experience across fintech, e-commerce, SaaS, logistics, EdTech, and defense tech.

M.Eng. in Control & Automation (with Honours). AWS Solutions Architect Professional. OSCP-certified. I build things that ship, scale, and stay up.

I am eager to leverage my specialized skills to deliver high‑quality technical solutions that propel your business forward.

I design and deliver backend-heavy, full-stack systems: high-throughput APIs, event-driven microservices, real-time IoT pipelines, payment and compliance integrations, and the React frontends that tie them together.

Primary stack:

• Turning fragmented ideas into a cohesive, scalable architecture that grows with your business
• Slow load times that lose leads before they even click
• Clunky UX that frustrates users and drives them away
• Broken mobile experience in an era where 55% of traffic comes from phones
• Security gaps that jeopardize customer data and trust
• Unreliable code that break the customer experience
• Refactoring legacy codebases and implementing best‑practice patterns to reduce maintenance overhead

1. +7% conversion rate and $5M in attributable revenue for an ed-tech platform (Lead Solution Engineer)
2. Payments live in 5 minutes - embedded fintech product with KYC, e-sign, EU VAT, and four transaction modes
3. SOX-ready real-time financial dashboard serving millions of requests without regressions
4. IoT command platform for electronic warfare units - dual WebSocket gateways, NATS JetStream, BullMQ, <2ms latency
5. Single codebase unifying SAML, SOAP, and ACH across a financial services integration layer
6. 70% reduction in tech debt on a legacy Rails monolith through targeted refactoring and architecture consolidation
7. 16-market content discovery engine, multi-tenant SaaS portals, biometric zero-trust auth, GPS-matched field auditing

37+ projects shipped across 13 years. Full mission log: azelenets.github.io

• Startups that need a senior engineer who can own the architecture, not just execute tickets.
• Scaleups dealing with legacy debt, integration complexity, or performance ceilings.
• Teams that need a reliable senior contributor without the overhead of a full hire.

I integrate fast - remote or on-site - and I align technical decisions with business goals before writing a line of code.

Freelance projects · Contract engagements · Full-time remote roles

Book a 30-minute call → Google Meet. No pitch. Just a direct conversation about what you're building.

Andrii Zelenets · Professional Software Engineer