Introduction
Overview.
I'm a Frontend Developer with 5+ years of commercial experience, specializing in React, Next.js, TypeScript, and Web3. I thrive on building high-quality, animated, responsive interfaces — from DeFi platforms and multi-chain wallet integrations, to payment systems, Chrome extensions, and embeddable widgets. What sets me apart is my background as a Business Administrator with an emphasis in systems. I don't just write code — I understand what businesses actually need, how money flows, and how technical decisions impact the bottom line. That bridge between tech and business is where I thrive. Based in Poland, open to remote B2B contracts worldwide.
Frontend Developer
React Native Developer
Web3 & DeFi Developer
UI/UX Focused
What I have done so far
Work Experience.
Frontend Developer
HoudiniSwap
- Built a Manifest V3 Chrome extension — featuring a side-panel swap UI with JWT-secured API integration — extending the capabilities of the main platform directly in the browser.
- Engineered a payment-link system enabling users to generate shareable, pre-configured swap links for seamless one-click transactions.
- Developed an embeddable widget playground allowing third-party sites to integrate HoudiniSwap's swap UI directly into their pages.
- Implemented GraphQL subscriptions for real-time quoting and live order tracking across multi-chain wallets (EVM, Solana, Bitcoin, Tron, Sui, TON).
- Developed smart contract interaction layers for token approval flows and transaction signing.
Frontend Developer
Unizen
- Analyzed and implemented high-end code solutions following best architectural practices and component structural development.
- Built user-friendly Web3 and DeFi interfaces using Next.js, Ether.js, Wagmi, and Reown (AppKit/WalletConnect).
- Implemented smooth UI/UX animations with Framer Motion and actively contributed to product design decisions.
- Worked with Zustand for state management and Tailwind CSS for scalable, responsive styling.
React.js Frontend Developer
Tryg / Tata Consultancy Services
- Developed a digital pregnancy product for Tryg (a major Scandinavian insurance company), deployed across 10+ subsidiaries and driving 10% customer growth.
- Leveraged React, TypeScript, and React Native to build high-quality, user-friendly web applications and embeddable widgets.
- Actively contributed to product design decisions, ensuring intuitive and efficient user interfaces.
- Implemented testing methodologies (Jest, Cypress) to ensure optimal performance and reliability.
- Utilized CSS3, Styled Components, and Material UI for fully responsive layouts.
Full-stack Developer
Freelance
- Planned and engineered RESTful web services to manipulate dynamic datasets using React and Ruby on Rails.
- Built landing pages, dashboards, and online applications, producing both visuals and content to meet project specifications.
- Conducted unit testing to deliver optimal browser functionality and employed best-practice coding standards.
- Trained and supervised junior team members on ongoing full-stack projects.
What others say
Testimonials.
"
I had the pleasure of working with Sergio at HoudiniSwap, and I can confidently say he's both a strong engineer and a great teammate. He brings solid…
@ Halil Atilla
Senior Frontend Developer at HoudiniSwap
"
Sergio is deeply passionate about his work and is a fantastic collaborator. When working with him, you can always rely on his support, being highly de…
@ Ganesh Singh
UI Engineer II at Cleartrip (Flipkart Group)
"
Sergio is a fantastic developer and is a pleasure to work with. We have spent a lot of time in the same team together while enrolled at a software dev…
@ Ryel Banfield
Founder & Lead Developer at RCB Software
Get in touch