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Sergii User

@sergiiuser1

Full Stack Engineer at Symbiotic building backend and smart contract systems for high-value DeFi operations.

Portugal
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At Symbiotic, I develop and maintain production backend and smart contract systems for high-value DeFi protocol operations. My work includes contract integrations, reward distribution, accounting flows, and secure payout mechanisms.

At Eoracle, I architected Node.js backend services and built React interfaces for blockchain applications, integrating frontend, backend, and on-chain components into a production application. I also built unit, integration, fuzzing, and invariant test coverage.

At Primex Finance, I developed Node.js services and trading bots, built dApp interfaces, and designed smart contracts for a cross-DEX margin trading protocol. Earlier, I led engineering for enterprise applications at Infopulse and developed enterprise frontend interfaces at Luxoft.

Experience

Work history, roles, and key accomplishments

SY
Current

Full Stack Engineer

Symbiotic

Aug 2025 - Present (1 year 2 months)

Developed and maintained production backend and smart contract systems supporting high-value DeFi protocol operations. Designed backend-facing contract integrations, reward distribution logic, accounting flows, and secure payout mechanisms.

EO

Full Stack Engineer

Eoracle

Mar 2024 - Aug 2025 (1 year 5 months)

Architected Node.js backend services for APIs, business logic, relayer integrations, and off-chain infrastructure. Built React frontend interfaces for blockchain applications, including wallet connections and smart contract interactions.

PF

Full Stack Engineer

Primex Finance

Jan 2022 - Feb 2024 (2 years 1 month)

Developed backend services and trading bots using Node.js to automate trading strategy execution. Built React-based dApp interfaces integrated with smart contracts and backend APIs.

NN

Smart Contract Engineer

Nerif Network

Apr 2021 - Feb 2022 (10 months)

Consulted on architecture for a blockchain-native identity and permission system.

SI

Full Stack Engineer

SimpleMarket

May 2020 - Dec 2021 (1 year 7 months)

Built an NFT marketplace on EOS, handling both contract and frontend work. Integrated full-stack infrastructure with real-time indexing.

Education

Degrees, certifications, and relevant coursework

National Technical University of Ukraine 'Kyiv Polytechnic Institute' logoNI

National Technical University of Ukraine 'Kyiv Polytechnic Institute'

M.Sc., Applied Mathematics

M.Sc. in Applied Mathematics from the National Technical University of Ukraine 'Kyiv Polytechnic Institute'.

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