Top Java Developer Jobs in London

Develop and maintain scalable Java applications, RESTful APIs, and integrations. Responsibilities include writing clean code, conducting code reviews, debugging, testing, optimizing performance, documenting solutions, and collaborating with cross-functional Agile teams.

Develop ultra-high-performance Java software for pricing, execution, and risk management in an algorithmic trading platform. Collaborate with quantitative researchers to implement scalable, highly available models and design distributed systems supporting 24x7 trading operations. Responsibilities include server-side development, software releases during live trading, and solving performance, reliability, and high-availability challenges.

Designs and maintains Java backend systems for MACH’s blockchain and DLT solutions. Responsibilities include developing REST APIs and microservices, integrating smart contracts, managing databases, implementing CI/CD pipelines, optimizing performance, troubleshooting issues, and collaborating with architects and cross-functional teams. The role also supports secure, scalable financial-services workflows and requires documentation of technical designs and processes.

Build scalable Java backend systems using Spring, REST APIs, microservices, databases, messaging, Docker, and cloud platforms. Lead architecture and technical design, promote engineering excellence, mentor engineers, drive delivery, improve automation, and evaluate emerging technologies and AI capabilities. Collaborate with clients and cross-functional teams to deliver secure, resilient software with measurable business value.

Design, develop, and maintain scalable backend systems for fintech products. Build REST APIs and microservices, improve existing systems, and support payments, treasury management, transaction booking, and crypto liquidity platforms. Use Java, PostgreSQL, and Spring Boot with clean code, TDD, DDD, and CI/CD practices. Collaborate with a high-performing team to deliver secure, maintainable products in a rapidly growing environment.

Design, develop, and maintain scalable backend systems for fintech products. Build REST APIs and microservices supporting card payments, treasury management, transaction booking, and crypto liquidity. Develop greenfield and existing systems using Java, Spring Boot, and PostgreSQL, while applying clean code, test-driven development, domain-driven design, and continuous integration and delivery.

Design, develop, and maintain scalable, secure backend systems for fintech products. Build REST APIs and microservices supporting card payments, treasury management, transaction booking, and crypto liquidity. Work primarily with Java, PostgreSQL, and Spring Boot while applying clean code, TDD, DDD, and CI/CD practices. Collaborate with a high-performing team on greenfield development and improvements to systems serving millions of users.

Develop and lead low-latency Java and Rust systems for algorithmic trading, market data replay, and backtesting. Build and optimize event-sourced microservices operating at 10–100 microsecond response times. Analyze complex processes, design application frameworks, integrate new products, and tune performance across the JVM, Linux kernel, and networking stack. Collaborate with senior stakeholders, document architectures, and mentor developers across Citi’s Markets Technology teams.

Build and maintain backend services and REST APIs using Java and Spring Boot. Write clean, tested code; work with relational and NoSQL databases; participate in code reviews; collaborate with senior engineers and product teams; and use Git-based CI/CD workflows to deliver features. The role includes mentorship, client collaboration, and occasional travel to client sites or company offices.

Design, build, operate, and evaluate secure backend services in a Java-based, event-driven microservices platform for high-volume, low-latency usage-based pricing. The role requires independent technical judgment, code quality and security assessment, and effective use of AI development tools. Preferred experience includes acquisition-related team integration, complex business logic, high-throughput systems, and documenting shared system context for reliable AI-assisted development.

Develop and test cloud-based full-stack applications and prototypes using Java, Spring Boot, Python, TypeScript, Angular, and Azure. Build REST APIs, integrate microservices and event-driven systems, create accessible responsive interfaces, contribute to CI/CD and automated testing, and apply secure coding practices. Collaborate with architects, data engineers, and UX designers during discovery-phase projects. The role requires active SC clearance and occasional travel to London.

Design and develop Java and Python applications, lead projects, and mentor junior developers. Ensure robust application testing and support production issues.

Design and build scalable backend features using Java and Spring Boot. Collaborate with cross-functional teams, lead complex projects, make technical decisions, balance feature development with technical debt, optimize performance and testing pipelines, and mentor junior engineers while delivering reliable solutions for millions of users.

Develop and maintain Java and Kotlin software for a collateral management platform supporting 24/7 trading. Contribute to distributed, real-time, event-driven systems; trading venue integrations; reference data frameworks; and accounting pipelines for traditional and digital assets. Debug production code, build new functionality, participate in code reviews, and collaborate with experienced engineers while learning financial market infrastructure.

Develop and enhance Java applications, translate complex requirements into technical specifications, and build scalable cloud-native solutions using Spring Boot, Kafka, AWS, and microservices. The role includes implementing architecture patterns, writing comprehensive automated tests, working with relational and non-relational databases, supporting CI/CD, addressing information security and data privacy requirements, and mentoring junior developers.

Develop and support an endpoint security product using Java, Node.js, TypeScript, and React. Investigate enterprise customer issues, debug complex systems, analyze logs, profile performance, and identify root causes. Collaborate with global Support, QA, Product, and Engineering teams, contribute to product roadmap decisions, and develop security solutions within an agile environment.

Develop and maintain Elasticsearch’s Inference API and plugin framework, integrating internal and external AI providers. Responsibilities include API and protocol design, streaming, asynchronous execution, rate limiting, configuration, billing integration, error handling, open-source contribution reviews, incident response, and comprehensive unit, REST, and rolling-upgrade testing. The role requires advanced Java expertise, concurrency and parallelism knowledge, API design skills, cross-functional collaboration, and autonomous work in a distributed team.

Design, build, test, and maintain scalable full-stack web applications and integrations using Java, Python, and React. Implement AI-enabled features, event-driven data pipelines, and marketing integrations (CDP/CRM/CMS). Improve code quality via AI-assisted tools, CI/CD, observability, and security/compliance best practices while collaborating with product, marketing, and partners.

Hands-on senior fullstack developer building backend-led JVM services (Kotlin/modern Java) and responsive React/TypeScript frontends. Design APIs, event-driven workflows, tests, CI/CD pipelines, observability, and contribute across discovery, deployment, production support, and technical decisions while validating AI-assisted tools where helpful.

Design, build, and optimize high-performance, low-latency Java services and protocols for exchange, matching-engine, and trading infrastructure. Develop order, session, instrument, and account models; create automated testing and benchmarking strategies; diagnose production issues; and support deployments. Collaborate with clients, SREs, QA, and leadership to deliver production-ready, observable systems and communicate technical trade-offs clearly.

Develop and troubleshoot secure, scalable Java applications in an agile environment. Design and implement solutions using Spring, Spring Boot, REST services, databases, and modern software development practices. Create architecture and design artifacts, investigate system logs, maintain production code, analyze data for reporting and continuous improvement, and support application resiliency, security, testing, and operational stability.

The role involves designing and building cloud-native applications using Java and Spring Boot, focusing on scalable microservices for financial institutions while leading agile practices.

Design, implement and evolve core components of a Java-based distributed runtime: cluster services, distributed data structures and execution engines. Work on partitioning, replication, coordination and recovery, write reliable low-latency production code, contribute to architecture, reviews and mentoring.

Develop core infrastructure and horizontally scalable APIs for Elasticsearch. Resolve complex performance and concurrency issues, improve cloud operations and observability, automate developer workflows, and support operational investigations. Lead cross-team projects, collaborate with open-source communities, and own technical designs and implementations from inception through delivery. Apply strong Java expertise, CI/CD practices, AI-assisted development, and distributed-team communication.

Lead and mentor an agile team to design, develop, secure, and operate scalable cloud-native applications using modern front-end tech and AI-assisted engineering practices; drive automation, code quality, resiliency, and operational stability.