zasulskii

(Golang, Rust, Next.js, TypeScript) Decentralized network, ID and verification ecosystem Designed and developed core systems, including backend microservices on Go, SSO and auth protocols, smart contracts on Solana with integrated oracle solutions. Participated in a full audit cycle of smart contracts. Built frontend apps using React and Next.js, integrating UI with backend APIs and blockchain services. Collaborated closely across teams to design system workflows, prepare UML diagrams, write protocol documentation, and ensure full coverage of testing for smart contracts and backend services.

(Golang, React, Next.js, Solidity, Node.js) Web3 development powerhouse & solutions hub Development of innovative DEX for trading tokens on the Bitcoin network, using Bitcoin Script + Lightning Network. Built the DeFi app using React with Next.js, utilizing crypto and hashing libraries to interact with Bitcoin. Architected AWS cloud environment utilizing CloudFront for Ingress Gateway for all internal services. Integrated AWS Amplify along with various cloud-based SaaS solutions to enhance and improve scalability with performance. Development of protocol for extra-earning from ETH Staking on Solidity, integration with Lido Protocol, led gas-optimization plan for smart contracts. Played a key role in preparing DeFi protocol and smart contracts for audit, organized test plan and accompanied the entire process for the auditors. Played a key role in writing integration test cases for Solidity smart contracts with 99% coverage, writing protocol documentation and developing UML diagrams for smart contracts.

(React, Node.js, TheGraph, Solidity, Nest.js) Decentralized protocol for borrowing/earning crypto tokens Developed core smart contracts on Solidity for cryptocurrency loans and prepared for audit, ensuring compliance with CertiK and Halborn security standards. Achieved over 95% test coverage with Hardhat. Migrated from traditional blockchain parsing to TheGraph, creating subgraphs that sped up data querying by 2x and improved reliability, removed the need for storage and databases, and made services stateless. Developed from scratch an authorization gateway through cryptocurrency wallets using Nest.js and APIs, which allowed the service to have fewer dependencies and not to use third-party solutions. Built and optimized backend services in Node.js for reliable smart contract interactions, caching results from the blockchain. Set up Docker to all services and clustering with Docker Swarm, which allowed rolling updates to be done in each release, removing the downtime on updates. Integrated Grafana+Prometheus+Loki stack for reports, metrics and alerts of the entire project ecosystem, set up notifications for critical events, handling user tickets and incidents.

(React Native, Node.js, PostgreSQL, Blockchain) Crypto-based decentralized messenger and open-source blockchain Developed market-making trading bot using Node.js, which includes functions of artificial scaling of volume for trading pairs on CEX/DEX exchanges, filling the bet, working with futures contracts. Integrated 15+ APIs from popular trading exchanges for the market-making bot, allowing users to trade and promote their tokens on leading exchanges. Developed a mobile application using React Native for a market-making trading bot. Integrated secure authentication protocol to protect user data and enabled cross-platform compatibility, supporting both iOS and Android devices. Led the optimization of Adamant nodes, achieving nearly a 2x increase in transaction requests performance. This required optimizing core SQL queries and using Redis for efficient caching, which reduced the average response time for REST API requests from 500 ms to less than 250 ms. Played a key role in development of new features for the Adamant blockchain. Designed and developed new transaction types from scratch to meet the evolving needs of the ecosystem.

(React, Node.js, NestJS, PostgreSQL) DDoS protection service, IT-infrastructures Played a key role in development of microservice infrastructure on Node.js and NestJS, database structure development, optimisation of core SQL queries, ensuring fast data access and requests under load. Developed and integrated a queue and lock system in notification service, data migrations, as protocol for messaging between microservices, which improved atomarity, stability and data synchronization. Developed from scratch an internal UI library using React, on which most of the company’s applications are built-on, enabling faster development across teams. Initiated and led the integration of CI/CD and TDD for services under our responsibility, set up CI/CD pipelines using Github Actions, integrated Docker and Docker Swarm, implemented load and unit testing with 90% coverage to ensure high-quality releases and reduce production issues. Conducted technical interviews and eventually selected several developers whose skills positively impacted the product.