Blockchain Software Developer

Citigroup; Greater London; Hybrid; GBP 62,000 - 102,000; Full time

Benefits offered by this job

27 days leave

Private medical care

Life insurance

Pension plan

Employee discounts

Learning and development resources

Hybrid work

Job summary

Citigroup in London is seeking a hands-on Web3 backend engineer to design, implement, and deploy blockchain components for an institutional platform. You will build backend services interfacing with public and permissioned networks and develop secure Solidity contracts with gas-aware optimizations.

Collaborate with architects and engineers to deliver scalable Web3 infrastructure, participate in code reviews, and stay aligned with Agile/Scrum practices within a distributed global team.

Qualifications

• Bachelor's degree in CS/Engineering; a masters degree is a plus
• Extensive software engineering experience with strong backend foundation
• Hands-on Web3 and blockchain app development incl. smart contracts
• Backend development experience with Java/Spring, Node.js or equivalent
• Solidity smart contract development with testing frameworks (Hardhat/Foundry/Truffle) and security best practices
• Experience with Web3 libraries (Web3J/Web3JS/Ethers.js/Viem)
• Understanding of blockchain fundamentals, consensus, gas models, key management
• Familiarity with token standards (ERC-20/721/1155/3525)
• Exposure to Layer 2 scaling and cross-chain interoperability is a plus
• Experience with asynchronous programming and event-driven systems
• DevOps familiarity: Docker, Kubernetes, CI/CD pipelines
• Knowledge of cryptography and secure on-chain development
• Experience in financial services or regulated industries is a plus
• Agile/Scrum experience and distributed team collaboration
• Strong Web3 stack knowledge from contracts to on-chain/off-chain integration
• Solid grounding in API design, microservices, data structures, algorithms
• Awareness of smart contract vulnerabilities and secure development practices
• Enthusiasm for Web3 and ability to learn new protocols quickly
• Strong communication with engineers, architects, and non-technical stakeholders
• Ability to manage delivery, prioritize, and meet sprint commitments
• Rigorous testing, code quality, and documentation
• Experience with Git, Jira, Jenkins, Hardhat/Foundry, Docker, Helm

Responsibilities

• Design, develop, and deploy Web3 components for the Digital Asset Platform
• Build and maintain backend services interfacing with blockchain networks
• Develop, test, and audit Solidity contracts ensuring security and gas efficiency
• Integrate Web3 libraries into enterprise Java/Node.js backends
• Implement asynchronous, event-driven architectures for on-chain events
• Collaborate with architects to design scalable Web3 infrastructure
• Participate in code reviews and provide constructive feedback
• Support integration of digital asset custody, tokenization, and DeFi/TradFi bridging
• Contribute to technical documentation and architecture notes
• Stay current with Web3 ecosystem, protocol upgrades, and tooling
• Work in Agile/Scrum within a distributed global team
• Help identify and resolve technical issues across the Web3 stack

Skills

Web3 development

Backend development

Java/Spring

Node.js

Solidity

Testing frameworks

Web3 libraries

Blockchain fundamentals

Docker

Kubernetes

CI/CD

Agile/Scrum

Team collaboration

Education

Bachelor's degree in CS/Engineering

Masters degree (plus)

Tools

Web3J

Web3JS

Ethers.js

Viem

Hardhat

Foundry

Truffle

Jira

Jenkins

Git

Docker

Kubernetes

Job description

Salary: £62,000 - 102,000 per year

Requirements:

• Bachelors degree in Computer Science, Engineering, or a related discipline; a masters degree is a plus
• Extensive overall software engineering experience with a strong backend development foundation
• Proven hands-on experience in Web3 and blockchain application development, including smart contract development and blockchain protocol integration
• Solid experience with backend development using Java/Spring, Node.js, or equivalent enterprise frameworks
• Proficiency in Solidity smart contract development, including testing frameworks such as Hardhat, Foundry, or Truffle, and security best practices
• Hands-on experience with Web3 libraries such as Web3J, Web3JS, Ethers.js, or Viem
• Solid understanding of blockchain fundamentals, including consensus mechanisms, transaction lifecycle, gas models, wallet infrastructure, and key management
• Experience with token standards such as ERC-20, ERC-721, ERC-1155, ERC-3525, or equivalent, and tokenization patterns
• Familiarity with blockchain networks such as Hyperledger Besu, Solana, or Canton is a strong plus
• Experience with asynchronous programming, event-driven systems, and message queuing such as Kafka or RabbitMQ
• Familiarity with DevOps practices, containerization such as Docker and Kubernetes, and CI/CD pipelines
• Understanding of cryptographic concepts such as digital signatures, hashing, PKI, and secure key management as applied to blockchain systems
• Exposure to Layer 2 scaling solutions and cross-chain interoperability protocols is a plus
• Experience in financial services or regulated industries is a plus
• Familiarity with Agile/Scrum methodologies and distributed team collaboration tools
• Strong command of the Web3 technology stack, from smart contract development to on-chain/off-chain integration patterns and blockchain node interaction
• Solid grounding in enterprise software engineering, including API design, microservices, data structures, algorithms, and design patterns
• Awareness of common smart contract vulnerabilities and best practices for secure on-chain development
• Genuine enthusiasm for the Web3 ecosystem and the ability to rapidly learn and apply new protocols, standards, and tooling
• Strong team player who communicates clearly and constructively with engineers, architects, and non-technical stakeholders
• Ability to manage personal delivery commitments, prioritize effectively, and produce high-quality output within sprint cycles
• Rigorous approach to testing, code quality, and documentation
• Working knowledge of engineering tools including Git, Jira, Jenkins, Hardhat/Foundry, Docker, Helm, and observability platforms

Responsibilities:

• Design, develop, and deploy Web3 components and integrations for our 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
• Develop, test, and audit smart contracts written in Solidity or equivalent languages, ensuring security, correctness, and gas efficiency
• Integrate Web3 libraries and SDKs into our 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 design scalable, secure, and resilient Web3 infrastructure
• Participate in code reviews and provide constructive technical feedback
• 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 evolving Web3 ecosystem, including protocol upgrades, new token standards, Layer 2 solutions, and emerging tooling relevant to institutional use cases
• Work within Agile/Scrum frameworks and participate 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

Technologies:

• API
• Backend
• Blockchain
• CI/CD
• DevOps
• Docker
• Git
• Helm
• Support
• JIRA
• Java
• Jenkins
• Kafka
• Kubernetes
• RabbitMQ
• Security
• Solidity
• Spring
• Web3
• microservices
• NodeJS
• Ethereum

More:

We are Citi, a global organization of more than 230,000 people, and we are building our Citi Integrated Digital Assets Platform engineering team in London. This is a hands‑on role focused on the intersection of decentralized technologies and institutional finance, where you will help us design and deliver production‑grade Web3 infrastructure for tokenization, smart contracts, on‑chain settlement, and blockchain integrations. You will join a collaborative, globally distributed team of engineers, architects, and business technologists, with access to continuous learning, internal innovation programs, and the opportunity to make a real impact on the future of digital finance. In London, we offer a business casual workplace with a hybrid working model of up to 2 days working from home per week, a competitive base salary reviewed annually, 27 days of annual leave plus bank holidays, discretionary performance bonus, private medical care and life insurance, an employee assistance program, pension plan, paid parental leave, employee discounts, and learning and development resources. We are committed to an inclusive workplace where everyone can thrive.

last updated 36 week of 2026