Aleksandar

Kostic

- Developed a real-time chat application using WebSockets and Node.js, handling 100,000+ concurrent users with a latency of under 50ms, ensuring a seamless messaging experience. - Redesigned the entire frontend architecture with Vue.js and Vuex, improving modularity and enhancing user engagement by 20% through a more intuitive UI. - Implemented JWT-based authentication and OAuth2 login integrations (Google, Facebook), enhancing user security and reducing unauthorized access incidents by 60%. - Refactored backend services by migrating from REST APIs to GraphQL, reducing over-fetching issues and cutting API response payload size by 40%, leading to faster app performance. - Automated DevOps workflows by setting up CI/CD pipelines with Docker and AWS CodePipeline, reducing deployment time from 30 minutes to under 5 minutes. - Integrated Redis caching mechanisms for frequently accessed database queries, decreasing load on MongoDB servers and reducing response times from 800ms to 150ms.

- Led the end-to-end development of a high-traffic web application serving over 1M users, optimizing frontend performance with Next.js server-side rendering (SSR) and reducing page load times by 50%. - Architected and implemented a scalable microservices infrastructure, migrating from a monolithic system to containerized Node.js services on AWS ECS, which improved system reliability and reduced downtime by 40%. - Optimized PostgreSQL database queries using indexing and partitioning techniques, improving read/write efficiency by 30% and reducing query execution time from 200ms to 50ms. - Designed and developed GraphQL APIs, reducing frontend-over-fetching issues and decreasing API response times by 35%, enhancing overall user experience. - Mentored a team of 5 junior developers, conducting code reviews and workshops on React best practices, TypeScript, and backend optimizations, resulting in a 20% improvement in overall code quality.

- Designed, developed, and audited smart contracts for DeFi platforms, NFT marketplaces, and DAOs, ensuring secure, gas-efficient, and upgradeable architectures while maintaining full EVM compatibility. - Deployed ERC-20 and ERC-721 token contracts, handling transactions exceeding $5M+ in total volume, and implemented automated liquidity pool mechanisms for a decentralized exchange (DEX). - Optimized gas costs in Solidity smart contracts by implementing bitwise operations, storage packing, and function modifiers, reducing average gas fees by 40% on Ethereum mainnet. - Integrated Chainlink oracles to enable real-time price feeds and data-driven smart contract executions, ensuring secure on-chain data verification for lending protocols. - Engineered a staking and rewards mechanism, allowing users to stake governance tokens in a decentralized voting system with APY adjustments based on network participation.

- Developed and deployed custom smart contracts for DeFi lending platforms, staking protocols, and NFT marketplaces, ensuring secure, gas-efficient, and scalable implementations. Conducted rigorous unit and integration testing using Hardhat and Chai to prevent security vulnerabilities. - Built and launched a feature-rich NFT minting platform that integrates IPFS for decentralized storage, ensuring metadata immutability and long-term accessibility. Implemented dynamic NFT metadata updates, allowing artists to modify NFT attributes post-mint based on predefined logic. - Conducted smart contract security audits, identifying and mitigating reentrancy attacks, integer overflows, and access control vulnerabilities. Provided comprehensive audit reports with risk assessments and mitigation strategies, leading to a 40% reduction in potential exploits before deployment.