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SR2 | Socially Responsible Recruitment | Certified B Corporation™
Senior Full Stack Engineer | Java | React | Outside IR35

Senior Full Stack Engineer | Java | React | Outside IR35

On site

London, United kingdom

£ 600 /day

Senior

Freelance

07-01-2026

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Skills

Java MongoDB GitLab CI/CD Docker Kubernetes Test Test Automation react Microservice Spring Maven Microservices

Job Specifications

Senior Full Stack Engineer | Java | React | Outside IR35
Java | React | Modernisation | DDD | Microservices | AI-Assisted Engineering

SR2 is supporting a consultancy-led delivery engagement focused on modernising large, complex software estates. This role suits a senior, hands-on Full Stack Developer who enjoys working closely to clients, reducing technical debt, and improving engineering practices across delivery teams.

You'll operate as a consulting engineer within a multi-disciplinary environment, helping teams move faster and more safely through modern development approaches, tooling, and AI-assisted engineering techniques.

The Role

This is a hands-on senior engineering role, focused on modernising Java/React applications, improving developer productivity, and guiding teams toward better architectural and delivery outcomes. You'll work closely with platform, test, and client engineering teams, while reporting into a Principal Engineer and influencing technical direction on delivery.

Key Responsibilities
Design and deliver modern Java/React applications within complex, Legacy-heavy environments
Modernise development practices to improve speed, quality, and reliability
Support the decomposition of monolithic systems into well-defined, maintainable services
Apply Domain Driven Design principles to improve system clarity and longevity
Collaborate with platform and test engineers on end-to-end delivery
Introduce and champion AI-assisted development practices where appropriate
Act as a senior consulting presence within delivery teams, influencing best practiceEssential
Strong hands-on experience with Java (Spring) Back End development
Strong experience with React and modern Front End engineering
Experience working with microservice-based architectures
Solid understanding and application of Domain Driven Design (DDD)
Full stack awareness and the ability to collaborate across disciplines
Comfortable working directly with clients and guiding technical decisions
Experience modernising or refactoring large, complex systemsDesirable
Experience with MongoDB
Test automation experience, including Playwright
Containerisation and orchestration experience (Docker/Kubernetes)
Build and dependency management using Maven
CI/CD experience using GitLab
Familiarity with the GOV.UK Design System/GovUK UI Framework
Interest or practical exposure to AI-assisted development toolingThe Details
Contract role
IR35 status: Outside
Duration: 6 months + extensions
Location: London ~1 day per weekIf you're a senior Java/React engineer who enjoys modernisation work and operating in a consulting-style delivery environment, please apply for immediate consideration.

About the Company

Built to Make an Impact. We exist to harness the power of recruitment to create meaningful change across the world. Our mission is simple but profound: to connect purpose-driven talent with industries that shape a better future. From driving innovation in Tech for Impact, advancing the global Clean Energy transition, to empowering Central Government Public Services, we are a Global Recruitment Group committed to making an impact and leaving a positive legacy. Why We Exist We believe recruitment should do more than fil... Know more