Java Web Developer

Square One Resources; Greater London; On-site; GBP 38,000 - 63,000; Full time

Job summary

Square One Resources is seeking a highly technical Java Web Developer to join a team in London. The role focuses on complex backend systems, high‑performance fintech platforms and evolving web applications.

You will design and implement Java services, work with Spring Boot, REST APIs, React integrations and maintain robust, scalable software. Responsibilities include debugging, performance tuning, Agile collaboration and delivering features in a fast-paced environment.

Qualifications

• Java is the core, with Spring-based backend development.
• REST API design, implementation and consumption.
• Experience with React for frontend integration is expected.
• SQL and relational databases experience (PostgreSQL).
• Git version control and Maven/Gradle build tools.
• Familiarity with Agile development practices and Linux environments.

Responsibilities

• Design, develop and implement robust Java backend services and web applications.
• Write clean, well-tested code following engineering standards.
• Participate in technical design with senior engineers and architects.
• Collaborate with frontend developers to integrate backend services.
• Investigate issues, debug and optimize performance.
• Break down user stories into technical tasks and deliver on time.
• Maintain existing systems and evolve platform capabilities.
• Promote strong team culture and cross-functional collaboration.
• Communicate technical concepts to diverse stakeholders.
• Stay current with Java, Spring, and software engineering best practices.

Skills

Java development

Spring Framework

Spring Boot 3.x

REST APIs

React

SQL

Git

Maven/Gradle

Agile development

Linux/Unix

Education

BS/MS in Computer Science or related

Tools

Docker

CI/CD

PostgreSQL

Job description

Job Title: Java Web Developer
Location: London 3x onsight
Rate: Up to £340 a day
Start Date: Mid September
Job Type: Contract 12 months

The Opportunity

A leading global financial technology organisation is looking for a highly technical, hands‑on Java Developer to join an established engineering team working on a sophisticated trade management and financial technology platform.

The organisation provides technology and infrastructure that supports participants across global financial markets. Its platform enables users to execute and manage trades across multiple asset classes and markets, manage risk throughout the trade lifecycle, connect with execution, prime and clearing brokers, and collaborate with a broad network of financial technology partners.

This is an exciting opportunity for a developer who enjoys working on complex backend systems, web applications and high-performance financial technology.

The successful candidate will contribute to the maintenance, enhancement and evolution of existing applications, while also helping shape new platform capabilities and user‑facing functionality.

Key Responsibilities

• Design, develop and implement robust Java backend services and web applications.
• Write clean, maintainable and well‑tested code in line with established engineering standards.
• Participate in technical design discussions alongside senior engineers and architects.
• Work closely with frontend developers to integrate backend services with web‑based user interfaces.
• Investigate and resolve technical issues, including debugging and performance optimisation.
• Break down user stories into technical tasks and deliver solutions within agreed timescales.
• Collaborate within an Agile engineering environment alongside product owners, QA engineers and other developers.
• Maintain and enhance existing systems while protecting application stability, performance and reliability.
• Contribute positively to team culture and build strong working relationships across engineering and product teams.
• Communicate technical concepts effectively to both technical and non-technical stakeholders.
• Keep up to date with modern Java, Spring, web development and software engineering practices.

Essential Skills & Experience

• Strong Java development experience, with Java 21 preferred.
• Excellent understanding of core Java concepts including collections, concurrency and memory management.
• Strong commercial experience with Spring Framework and Spring Boot 3.x.
• Experience designing, developing and consuming REST APIs.
• Good knowledge of React, ideally React 17, and integrating frontend applications with backend services.
• Strong understanding of web application architecture and client‑server communication.
• Experience working with SQL and relational databases, such as PostgreSQL.
• Proficiency with Git and build tools including Maven or Gradle.
• Strong focus on clean code, automated/unit testing and code reviews.
• Experience working within Agile development environments.
• Comfortable working in Linux/Unix environments.
• Approximately 4-8 years of commercial software engineering experience.

Desirable Skills

• Experience working with JSF, JSP or other legacy Java UI technologies.
• Familiarity with modern frontend development and component‑based architectures.
• Experience with CI/CD pipelines and automated testing.
• Exposure to Docker and containerisation.
• Understanding of distributed systems and related architectural concepts.
• Familiarity with the wider Spring ecosystem and associated tooling.
• Previous experience within financial services, capital markets, trading or other high‑volume transaction platforms.

Education

A BS/MS in Computer Science, Software Engineering or a related discipline, or equivalent commercial software engineering experience.

Why Consider This Opportunity?

You'll be joining a technically strong engineering environment where you can work on complex, business‑critical systems used within global financial markets.

The role offers the opportunity to work across modern Java backend technologies, web applications, APIs and distributed systems, while contributing to the ongoing development of a sophisticated trading technology platform.

This is a confidential opportunity. Further details regarding the organisation, team structure and platform will be provided during the recruitment process.

Square One embraces diversity and will treat everyone equally. Please see our website for our full diversity statement.