Java/Kotlin Developer | Hybrid, London | Inside IR35

Korn FerryCity, London🇬🇧United KingdomPosted 19 Oct 2026

Why This Role Stands Out

Leverage your Java/Kotlin expertise to build critical backend services for a leading financial institution, offering a competitive daily rate and the flexibility of a hybrid London-based role. This is an excellent opportunity for a mid-senior developer passionate about creating high-performing, scalable APIs and contributing to impactful mobile applications within a collaborative environment. Apply now to enhance your skills and gain valuable experience in a dynamic industry.

Quick Overview

Seniority

Mid Senior

Employment type

Temporary/Casual

Work mode

Hybrid

Location

City, London, United Kingdom

DockerScalaGraphQLJavaKotlinKubernetes

Job Description

Role: Java/Kotlin Developer (Backend Mobile)

Location: Hybrid, City of London, 3 days per week

Contract: 12-month contract

Industry: Financial Services

IR35 determination: Inside

Rate: up to £400 per day

Responsibilities

Design, develop, and maintain the mobile service layer (Backend-for-Frontend) supporting large-scale mobile applications
Deliver secure, reliable, and high-performing Server Side APIs for Real Time consumer experiences
Write clean, maintainable code and contribute to code reviews, refactoring, and continuous improvement initiatives
Collaborate with mobile, product, and design teams to define solutions that enhance usability and functionality
Troubleshoot and optimize application performance for responsiveness and scalability
Create robust unit tests and integration tests to ensure software reliability
Manage asynchronous processing, error handling, and performance optimization in distributed systems
Support Legacy system integrations and modernize existing codebases when required
Follow CI/CD best practices and contribute to team development pipelines and build systems
Actively share ideas, propose improvements, and participate in solution design discussions

Requirements (Must Have Skills)

Proven experience building Server Side applications with strong understanding of modern Back End development practices
Proficiency in Kotlin or related JVM languages (Java, Scala, etc.)
Practical knowledge of RESTful and GraphQL (GQL) API design and integration
Hands-on experience with Gradle or similar build tools
Solid understanding of asynchronous programming, thread management, and performance optimization
Experience working with CI/CD pipelines and automated testing frameworks
Strong debugging and problem-solving skills with attention to system scalability and maintainability

Nice to Have Skills

Experience designing or integrating RAML-based documentation into API workflows
Familiarity with Legacy system modernization or integration within enterprise environments
Understanding of cloud-native development patterns or containerized deployment workflows (eg, Docker, Kubernetes)