Software Development Full-Stack

Liam Harkin

Senior Blockchain Engineer

**************@*****.*** Dublin, Ireland

https://www.linkedin.com/in/liam-harkin-345373360

Profile

Experienced blockchain engineer with a strong focus on cross-chain interoperability, smart contract development, and DeFi infrastructure. Skilled in building modular, secure, and scalable systems using Solidity, Rust, and Move across EVM and non-EVM chains. Proven track record in delivering decentralized trading platforms, NFT marketplaces, and bridging solutions with robust system design and DevOps practices. Adept at integrating backend services, SDKs, and real-time indexing for high-performance dApps. Passionate about protocol efficiency, developer experience, and full-stack blockchain architecture.

Skills

Blockchain Technology

Bitcoin, Ethereum, Solana, Aptos, Layer2

solutios, Consensus, P2P messaging, Zero

Knowledge, Cryptography, Hyperledger, Cosmos

SDK

Others

Sequencer, RPC, CI/CD, AWS, Azure, GCP, Geth

Tools

Tenderly, Remix IDE, The graph, IPFS, Alchemy

Language

C++, Rust, Go, Solidity, Vyper, Move, Python,

Javascript, Typescript, Java

Frameworks & Libraries

Hardhat, Foundry, Web3.js, Ether.js,

OpenZeppelin, Substrate, React.js, Next.js,

Express.js, Nest.js

Professional Experience

Senior Blockchain Engineer, Li.Fi 02/2023 – 04/2025 Berlin, Germany

•Designed and implemented modular smart contracts enabling cross-chain asset swaps, decentralized messaging, and high-efficiency transaction routing across multiple blockchain ecosystems.

•Designed and optimized bridge infrastructure, enabling secure, scalable transfers of assets and data across multiple L1s and L2s, incorporating fail-safes, relayers, and liquidity management.

•Developed and maintained Solver logic, responsible for route optimization, quote resolution, and execution batching, balancing gas efficiency, latency, and capital usage in dynamic environments.

•Contributed to full-stack system design, bridging on-chain logic with off-chain services including SDKs, transaction builders, backend APIs, and indexers.

•Led the development of a full-featured SDK, providing extensible APIs, type-safe interfaces, and integration hooks to support seamless adoption by external developers and partner platforms.

•Engineered scalable, real-time event streaming infrastructure - SolStream to process and index on-chain activity across diverse networks, powering dashboards, monitoring systems, and protocol logic.

•Developed smart contracts using Solidity, Rust, and Move, building for both EVM-based chains

(Ethereum, Arbitrum) and non-EVM platforms (Solana, Aptos, Sui) with a deep focus on performance, security, and composability.

•Implemented multi-message aggregation mechanisms, allowing atomic execution of complex multi-chain transactions, reducing costs and improving execution reliability.

•Automated deployment and testing workflows through robust CI/CD pipelines, leveraging tools like Docker, GitHub Actions, Hardhat, and Foundry to accelerate development and maintain security standards.

Blockchain Developer, Futureswap 05/2021 – 02/2023 California, US

•Spearheaded the development of core blockchain components for Futureswap, a decentralized trading platform enabling up to 30x leverage on Ethereum and Arbitrum.

•Designed and implemented robust margin trading mechanics, liquidation logic, and position tracking, enabling a secure and composable DeFi leverage ecosystem.

•Integrated Uniswap V3 for optimal swap routing and on-chain liquidity, enabling seamless execution of leveraged trades with minimal slippage.

•Developed an on-chain data explorer to visualize protocol analytics (open interest, positions, funding rates) and user-specific trade history.

•Built and deployed custom subgraphs using The Graph, enabling efficient querying of trading data and enhancing UI responsiveness.

•Collaborated on the architecture and design of a highly modular smart contract system, separating trading logic, asset management, and oracle integrations for security and upgradability.

•Contributed to the system design of our backend and data pipeline, integrating real-time market feeds, Chainlink oracles, and subgraph sync services for precision in trade execution and analytics.

•Implemented DevOps practices using Docker, Terraform, and AWS for scalable smart contract infrastructure, testnets, and monitoring environments. Full Stack Blockchain Developer, Quidd 02/2019 – 05/2021 New York, US

•Developed and deployed Solidity smart contracts for decentralized applications, including a cross- chain NFT marketplace leveraging IPFS for decentralized storage.

•Participated in development of the cross-chain and batch minting NFT for gas optimization using ONFT721A that is inherited from ONFT721 and Layer Zero Protocol.

•Architected and implemented DEX frontends and user interfaces, ensuring seamless integration with underlying protocols using Ethers.js, Web3.js, and custom contract abstractions.

•Built and integrated ERC-20 and ERC-721/1155 token contracts, including governance tokens, utility tokens, and custom permissioned tokens.

•Created responsive, performant frontend apps using React.js, Next.js, and Web3.js / Ethers.js, ensuring smooth on-chain/off-chain data sync.

•Handled end-to-end DevOps responsibilities: CI/CD pipelines, containerization (Docker), cloud deployment (e.g., AWS, GCP), and blockchain node management. Full Stack Developer, The Scalers 05/2017 – 02/2019 Dublin, Ireland

•Contributed to the development of scalable enterprise applications using React.js, Next.js, and Redux, enhancing UI/UX and optimizing component reusability.

•Assisted in building RESTful APIs with Nest.js and Express.js, ensuring efficient data handling and improved API response times.

•Developed authentication and authorization features using JWT and OAuth, ensuring secure access to web applications.

•Integrated third-party APIs and webhooks, improving real-time data synchronization and system interoperability.

•Participated in Agile development cycles, attending stand-up meetings, sprint planning, and contributing to team discussions.

•Assisted in CI/CD pipeline automation, reducing deployment times and improving workflow efficiency.

Education

Bachelor's Degree/Computer Science,

University College Dublin

04/2013 – 04/2017 Dublin, Ireland

Contact this candidate