
John McLaughlin
Verified Expert in Engineering
Blockchain Developer
New York, NY, United States
Toptal member since September 12, 2022
John is a full-stack blockchain developer with 10+ years' experience, deploying 150+ Solidity smart contracts (ERC-20/721/1155) across Ethereum, Polygon, Arbitrum, and zkSync. He brings deep Solana and Rust expertise (tokens, staking, DEX integrations) and builds multi-exchange trading platforms with real-time pipelines. John also builds AI into apps and connects it to live tools and data so it can act on its own.
Portfolio
Experience
- Web3 - 10 years
- Solidity - 9 years
- Docker - 9 years
- RESTFul APIs - 5 years
- Next.js - 5 years
- Amazon Web Services (AWS) - 5 years
- Solana - 4 years
- LLM Integration - 2 years
Preferred Environment
React, Next.js, Solidity, Web3, IPFS, Docker, Ethereum Virtual Machine (EVM), Amazon Web Services (AWS), Solana, LLM Integration
The most amazing...
...application I've built is Decent Portfolio, a peer-to-peer, local-first crypto portfolio tracker with no central server, on OrbitDB, IPFS, and libp2p.
Work Experience
Blockchain and Rust Developer
JoyPixels Inc
- Developed cross-platform desktop emoji picker using Tauri v2, Rust, and Vue with global keyboard shortcuts, system tray integration, and dual-window architecture for seamless emoji insertion.
- Eliminated external cliclick dependency by migrating to Tauri's native cursor_position() API, reducing installation complexity and improving reliability across macOS systems.
- Replaced clipboard-based emoji insertion with direct keystroke injection using macOS Core Graphics API, preserving user clipboard contents during emoji insertion.
- Implemented target app detection using AppleScript to capture display names instead of process names, ensuring accurate emoji delivery to VS Code, Sublime Text, and browsers.
- Built production macOS distribution packages (.app and .dmg), resolving Tauri version mismatches and documenting the build process for team handoff.
Blockchain Solana and Rust Developer
JoyPixels Inc
- Designed and deployed multiple versions of a Solana NFT program using Rust, implementing core minting functionality and emoji-based domain logic.
- Built and integrated validation logic to ensure the uniqueness of emoji array combinations, preventing duplicate NFT minting on-chain.
- Created a front-end reservation system for NFT acquisition, providing streamlined user experience for token minting and emoji domain registration.
- Deployed program iterations to the Solana blockchain, handling on-chain asset storage and transaction processing.
Blockchain Developer
All American Consultants LLC
- Architected and deployed a custom fungible token to the Solana mainnet, implementing tokenomics and establishing initial distribution infrastructure.
- Built full-stack liquid staking protocol with Rust smart contracts and React front end, enabling token holders to earn rewards through on-chain staking mechanisms.
- Created and deployed a sought-after NFT collection of 1,000+ unique digital assets, achieving strong secondary market trading volume and community adoption on Magic Eden marketplace.
- Developed proprietary marketplace program and web interface for project-specific NFT trading, implementing on-chain escrow and settlement logic.
- Integrated Discord authentication system with on-chain verification, restricting community access based on SPL token or NFT ownership.
- Executed social media campaign strategy to drive platform awareness, grow engaged user base, and facilitate organic community expansion across multiple channels.
- Designed and deployed an on-chain governance program enabling token-weighted voting on community proposals, establishing a decentralized decision-making framework.
Blockchain Developer
G.W. Pastrick Enterprises LLC
- Designed and developed an application to store encrypted academic records as on-chain NFTs where relevant stakeholders can retrieve these documents.
- Designed and developed a REST API where users can retrieve and decrypt user data by scanning a code.
- Designed a system where academic records can be uploaded in bulk and minted as NFTs through an NFT factory.
Python Developer (via Toptal)
Lucas Flett
- Designed and developed a Python-based trading bot connector for decentralized and centralized cryptocurrency exchanges, optimizing execution speed and transaction efficiency.
- Created a custom Telegram UI that allowed users to start trading bot scripts, submit algorithm-based orders, and monitor execution status directly within the exchange account UI.
- Conducted detailed code reviews for team members by evaluating GitHub pull requests, ensuring code quality and alignment with project standards before repository updates.
- Researched and analyzed 3rd-party asset custody solutions to determine optimal integration strategies for enhanced platform security and compliance.
Full-stack Blockchain Developer
Mueller Health Foundation, Inc
- Developed minting of on-chain NFTs to represent documents stored on the TBConnect app related to tuberculosis research and analysis.
- Upgraded overall application from Node.js 8 to Node.js 16 and React 16 to React 17 in 2023. Upgraded dependencies and cleared all errors to improve overall performance.
- Deployed the upgraded back-end to an AWS EC2 instance, the front-end to an AWS S3 bucket, and various APIs to Amazon API Gateway. As a result, the application is now fast, scalable with resizable compute capacity, highly secure, and very efficient.
- Upgraded the chat and virtual meeting functionality from Twilio Video to the Zoom Video SDK to enable group meetings instead of one-to-one sessions.
- Updated the visual aesthetic of the front end to enhance the overall user experience, making it more intuitive, engaging, and visually appealing.
Web3 Back-end Developer
Polemarch LLC
- Developed an Ethereum NFT marketplace for listing Bitcoin ordinal inscriptions with full function to create, mint, and list EVM NFTs representing inscribed Bitcoin ordinals, BRC-20 tokens, and name inscriptions.
- Contributed to the smart contract Solidity smart contract behind the NFT marketplace featured createNFT, listNFT, cancelListing, addToCart, burn, and other relevant functions.
- Worked on the contract design that utilized OpenZeppelin audited contract library to ensure safety and security.
- Designed and developed a REST API for storing Bitcoin inscription off-chain data such as collection value, curation, real-time pricing of listed NFTs in terms of ETH/USD, etc. The API utilized MongoDB for storage.
Blockchain Developer
Levi Sirmons
- Developed an Ethereum wallet that removed and added specific functionalities to the basic Metamask web3 wallet.
- Added permissions to the web3 wallet where it can be used by team members who do not possess administrative rights and permissions to the firm's treasury wallet(s).
- Created a web3 wallet browser extension distribution that can be uploaded into Chrome, Firefox, or Brave.
- Assisted in designing a team workflow that allows for close supervision of trading strategies by platform administrators.
Blockchain Developer
Currentz Corp.
- Worked as the lead blockchain developer for Currentz. Designed, developed, and deployed ER-C721 and ERC-1155 Solidity smart contracts for the Ethereum and EVM-compatible blockchains.
- Created a defined process for the team to set up NFT drops with a user interface for customers to mint and claim NFTs from their creative economy platform.
- Integrated not only Web 3.0 payments using cryptocurrencies through a Metamask wallet but also purchasing the NFTs using a credit card where customer knowledge of Web 3.0 is not necessary.
- Deployed contracts on Layer 2 chains such as Polygon or Optimism to allow the platform and its customers to save transaction "gas fees" when using cryptocurrencies.
Senior Blockchain Developer
John Nesgoda - Web3 Startup
- Developed an Ethereum Solidity smart contract with tokenomics functionalities.
- Implemented multi-signature wallet functionality as a method of custody.
- Added payment streaming functionality to multi-signature wallet orchestration.
- Designed and deployed a platform membership NFT token with an expiration date and the functionality to extend the expiration date.
Lead Blockchain Developer
McKurz Capital Incorporated
- Founded McKurz as a part-time development shop for Web3 applications, submitting our apps to 11 ETHGlobal and two Chainlink hackathons. Several of these apps won prizes in hackathon competitions and the interest of venture capital firms.
- Built Ethereum smart contract web apps using development tools such as Truffle and Hardhat, with React and Next.js as front ends.
- Deployed an NFT factory/marketplace to the Polygon blockchain during the ETHGlobal DAOHacks hackathon.
- Developed a few storage apps deployed to the Filecoin blockchain that were submitted to hackathons last year, including Disco Rock Repo for the 1960s to 1990s disco, rock, and pop music and Fin File Crypto for crypto investment videos and documents.
Adjunct Lecturer
CUNY-College of Staten Island
- Instructed on personal finance, using accounting software such as Microsoft Excel and QuickBooks.
- Led students on financial topics through a technology lens to better equip them for the 21st-century digital economy.
- Lectured on the history of blockchain, industry trends, and investing analysis into various projects such as Bitcoin, Ethereum, Solana, decentralized finance protocols, and NFTs.
Teacher
New York City Department of Education
- Taught mathematics topics such as basic algebra, intermediate algebra and trigonometry, and logic and pre-calculus.
- Instructed entrepreneurship students about website development using HTML, CSS, and JavaScript.
- Expanded student knowledge to extend JavaScript development to Node.js, React, and Next.js, with additional topics toward server-based development.
- Introduced students to blockchain history and use cases, the theory on Ethereum smart contracts, and the potential of cryptocurrency-based applications.
Experience
Trustworthy LLM Document Extraction (Grounding and Arithmetic Verification)
https://document-extraction-coral.vercel.app/Solana Liquidity Staking Pool App
https://mckurz-liquid-staking.vercel.app/This Solana DevNet liquid staking pool lets users stake SOL while maintaining liquidity via placeholder staking tokens. Users earn staking rewards, which can be claimed anytime. The app features an intuitive UI with deposit, withdrawal, reward claim functions, real-time pool, and user wallet stats.
FEATURES
• Stake and earn: Deposit SOL, receive liquidity tokens, and earn rewards.
• Claim rewards: Withdraw accumulated staking rewards anytime.
• Withdraw anytime: Unstake and reclaim original SOL.
• Live pool stats: Displays total deposits, rewards, and user balances.
• User-friendly UI: Simple deposit, withdrawal, and claim functions.
LIMITATIONS AND BEST PRACTICES
• Keep deposits small (approximately 0.50 SOL or less) for successful transactions.
TECH STACK
• Front end: Vite, React, Tailwind CSS
• Back end: Solana Web3.js, Anchor
• Smart contracts: Rust (Solana Program Library)
This project highlights my expertise in Solana smart contracts, decentralized finance apps, and Web3 front-end development with Vite for fast performance.
To connect to this application, you must have a Phantom or Solflare wallet funded with Solana Devnet tokens. You can visit https://faucet.solana.com/ to acquire SOL Devnet tokens.
Decentralized Database Crypto Portfolio Tracker
https://decent-portfolio.vercel.app/Technologies: Next.js 16, React 19, TypeScript, Tailwind, OrbitDB v2, Helia, libp2p, Node.js, Cloudflare Tunnel, Vercel.
EVM DeFi Staking Platform
https://mckurz-evm-staking-ui.vercel.app/Developed a complete DeFi staking application on Base Sepolia that allows users to stake MckurzToken (MKT) and earn 17.16% APR. Built with React, Ethers.js, and Solidity smart contracts.
KEY ACHIEVEMENTS
• Engineered a precision-based reward system using Solidity with customizable APR settings.
• Built a responsive React UI with real-time staking metrics, MetaMask integration, and intuitive stake and unstake functionalities.
• Resolved critical precision issues in reward calculations to ensure accurate APR display and reward distribution.
• Fixed mathematical discrepancies between displayed rates and actual reward accumulation.
• Implemented proper TVL tracking and reward projections.
• Optimized contract interactions to minimize gas costs while maintaining accurate rewards.
• Verified contracts on BaseScan with proper documentation.
TECHNOLOGIES
Solidity, React, Ethers.js, OpenZeppelin, Foundry, Base (Ethereum L2)
The project demonstrates my expertise in DeFi platform development, addressing complex tokenomics challenges while delivering an intuitive user experience with reliable on-chain performance.
To use this application, you must connect a Metamask wallet and connect to the Base Sepolia network.
Solana DeFi Trading Bot - Automated Token Analysis and Trading System
Key features:
• Real-time token detection and price analysis.
• Multi-factor trading decision system considering price movements, volume, and market momentum.
• Configurable risk management with price thresholds and volatility analysis.
• Automated buying and selling with slippage protection.
• Long-term holding mode for promising tokens.
• Comprehensive logging and transaction tracking.
• Robust error handling and retry mechanisms.
• WebSocket integration for real-time blockchain monitoring.
The bot is built using Python and integrates with Solana's blockchain infrastructure, demonstrating expertise in decentralized finance development, algorithmic trading, and blockchain technology.
Solana NFT Marketplace
https://black-kitten-solana-nft.vercel.app/marketplaceNature NFTs Marketplace
https://nature-nfts-marketplace-polygon.vercel.app/Legal Documents Marketplace
Decentralized Token Exchange
https://mckurz-dex.vercel.app/Safe Harbour Finance Reward Coin Staking App Deployed to zkSync
https://safeharbour-finance.vercel.app/Education
Master's Degree in Education Administration
City University of New York (CUNY) - Hunter College - New York City, New York, United States
Master's Degree in Mathematics Education
City University of New York (CUNY)-Brooklyn College - New York City, New York, United States
Bachelor's Degree in Accounting, Business Management, and English
St. John's University - New York City, New York, United States
Certifications
AWS Certified Developer – Associate
Amazon Web Services
AWS Partner: Accreditation (Technical)
Amazon Web Services Training and Certification
ConsenSys Certified Ethereum Developer
ConsenSys Academy
LFS171x: Introduction to Hyperledger Blockchain Technologies
The Linux Foundation | via edX
The Python Mega Course: Build Ten Real World Apps
Udemy
Modern React with Redux
Udemy
Codecademy Intensive Program: Build Front-end Web Apps from Scratch
Codecademy
Docker Mastery: The Complete Toolset From a Docker Captain
Udemy
Skills
Libraries/APIs
React, Node.js, Web3.js, Twilio API, Vue, Telegram Bot API, Auth, OpenZeppelin, Solana.py, React Redux, Libp2p, Pydantic
Tools
Microsoft Excel, MetaMask, Excel 2010, Git, GitHub, Ganache, Remix IDE, Claude Code, Docker Compose, Docker Swarm, Docker Hub, Zoom, MATLAB, Excel 2013
Languages
Solidity, JavaScript, HTML, CSS, HTML5, Rust, Python, TypeScript, Python 3, Python 2, Markdown, AppleScript
Frameworks
Next.js, Truffle, Hardhat, Flask, Anchor, Redux, gRPC, Tauri
Paradigms
DevOps, Microservices Architecture, Distributed Computing, UI Design
Platforms
Docker, Linux, Ethereum, Hyperledger, Windows, Blockchain, Decentralized Exchanges (DEXs), Blockchain Platforms, Amazon Web Services (AWS), DigitalOcean, AWS Cloud Computing Services, Hyperledger Fabric, Netlify, Twilio, Azure, Vercel, Kubernetes, MacOS
Storage
MySQL, Databases, PostgreSQL, MongoDB, Docker Cloud, Redis
Industry Expertise
Binance Cryptocurrency Exchange, Cybersecurity
Other
Web3, Ethers.js, Distributed Team Management, Instruction & Coaching, Time Management, Infura, Non-fungible Tokens (NFT), Decentralized Finance (DeFi), Ethereum Smart Contracts, Ethereum Test Network, Google Drive, Technical Writing, Smart Contracts, Blockchain & Cryptocurrency, Full-stack, ERC-20, Multisig, Blockchain Design, Decentralized Autonomous Organizations (DAO), zkSync, OpenSea, Bitcoin, CTO, Electronic Payments, Fraud Prevention, Cryptocurrency Wallets, Payment APIs, Fintech, Branding, Cryptocurrency, Decentralized Systems, Web 3.0, Fintech Consultant, Foundry, Polygon, Cloud, Crypto, Security, IT Security, Advisory, Strategy, Back-end Development, Web Development, AWS Partner Network (APN), APIs, Troubleshooting, Data Queries, Writing & Editing, Pulse Width Modulation (PWM), Ethereum Virtual Machine (EVM), Tokenomics, Software Architecture, Technical Leadership, Leadership, DApps, Cryptography, Computer Science, White Papers, Solana, Project Consultancy, Arbitrage, Use Case Analysis, Metaplex Sugar, Metaplex Candy Machine, Tokenization, RPC, WebSockets, Audits, Telegram Bots, API Integration, User Interface (UI), User Experience (UX), Back-end, Uniswap, Architecture, Stablecoins, ICO, VRF, Blockchain Development, Cloudflare, AI Agents, Agentic AI, RESTFul APIs, Artificial Intelligence (AI), AI Integration, API Design, High Code Quality, LLM Integration, Data Modeling, Mapping, Mentorship, Systems Design, Compliance, IPFS, CSS5, Arbitrum, Govtech, Mobile Advertising, Blockchain as a Service, GPU Computing, substream, TradingView, Large Language Models (LLMs), Filecoin, Intuit QuickBooks, K-12 Education, Business, Mathematical Finance, Personal Finance, Excel 365, HD Wallets, NFT Design, Token Design, Vite, Discord, OrbitDB, Helia, Prompt Engineering, FastAPI, Railway
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