Senior Blockchain Developer - Web3 Components and Smart Contract Integration

Role: Blockchain Developer

Location: New York, NY/Jersey City, NJ

Position Type: Fulltime

Key Responsibilities

• Design, develop, and deploy Web3 components and integrations for Citi's Digital Asset Platform, including smart contracts, on-chain event listeners, wallet integrations, and blockchain protocol connectors
• Build and maintain backend services that interface with public and permissioned blockchain networks (e.g., Ethereum, Hyperledger Besu, Corda, or equivalent)
• Develop, test, and audit smart contracts written in Solidity or equivalent languages, ensuring security, correctness, and gas efficiency
• Integrate Web3 libraries and SDKs (e.g., Web3J, Web3JS, Ethers.js, Viem) into enterprise Java and/or Node.js backend services
• Implement asynchronous, event-driven architectures to handle on-chain events, transaction lifecycle management, and blockchain state synchronization
• Collaborate with architects and senior engineers to contribute to the design of scalable, secure, and resilient Web3 infrastructure

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• Participate in code reviews, providing and receiving constructive technical feedback to maintain high engineering standards
• Support the integration of digital asset custody solutions, tokenization frameworks, and DeFi/TradFi bridging components
• Contribute to technical documentation, including smart contract specifications, integration guides, and architecture notes
• Stay current with the rapidly evolving Web3 ecosystem — tracking protocol upgrades, new token standards, Layer 2 solutions, and emerging tooling relevant to institutional use cases
• Work within Agile/Scrum frameworks, participating in sprint planning, stand-ups, and retrospectives within a distributed global team
• Help identify and resolve technical issues across the Web3 stack, escalating where appropriate to ensure delivery quality and timelines

Qualifications / Experience

• Bachelor's degree in Computer Science, Engineering, or a related discipline; MS is a plus
• 8+ years of overall software engineering experience, with a strong backend development foundation
• 2 to 4 years of hands-on experience in Web3 and blockchain application development, including smart contract development and blockchain protocol integration

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• 3 to 5 years of experience with backend development using Java/Spring, Node.js, or equivalent enterprise frameworks
• Proficiency in Solidity smart contract development, including testing frameworks (Hardhat, Foundry, Truffle) and security best practices
• Hands-on experience with Web3 libraries such as Web3J, Web3JS, Ethers.js, or Viem
• Solid understanding of blockchain fundamentals — consensus mechanisms, transaction lifecycle, gas models, wallet infrastructure, and key management
• Experience with token standards (ERC-20, ERC-721, ERC-1155, ERC-3525, or equivalent) and tokenization patterns
• Familiarity with permissioned blockchain networks (Hyperledger Besu, Fabric, Corda, or R3) is a strong plus
• Experience with asynchronous programming, event-driven systems, and message queuing (Kafka, RabbitMQ, or equivalent)
• Familiarity with DevOps practices, containerization (Docker, Kubernetes), and CI/CD pipelines
• Understanding of cryptographic concepts — digital signatures, hashing, PKI, and secure key management — as applied to blockchain systems
• Exposure to Layer 2 scaling solutions (Polygon, Optimism, zkSync, etc.) and cross-chain interoperability protocols is a plus
• Experience in financial services or regulated industries is a plus

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• Familiarity with Agile/Scrum methodologies and distributed team collaboration tools

Competencies / Skills

• Web3 Engineering Depth: Strong command of the Web3 technology stack — from smart contract development to on-chain/off-chain integration patterns and blockchain node interaction
• Backend Engineering Fundamentals: Solid grounding in enterprise software engineering — API design, microservices, data structures, algorithms, and design patterns
• Security Mindset: Awareness of common smart contract vulnerabilities (reentrancy, front-running, integer overflow, etc.) and best practices for secure on-chain development
• Curiosity & Adaptability: Genuine enthusiasm for the Web3 ecosystem and the ability to rapidly learn and apply new protocols, standards, and tooling
• Collaborative Spirit: Strong team player who communicates clearly and constructively with engineers, architects, and non-technical stakeholders
• Delivery Orientation: Ability to manage personal delivery commitments, prioritize effectively, and produce high-quality output within sprint cycles
• Attention to Detail: Rigorous approach to testing, code quality, and documentation — particularly important given the immutable nature of on-chain deployments
• Tooling Proficiency: Working knowledge of engineering tools including Git, Jira, Jenkins, Hardhat/Foundry, Docker, Helm, and observability platforms