Java/Kotlin Developer | Hybrid, London | Inside IR35

Korn Ferry; City Of London; On-site; GBP 70,000 - 100,000; Full time

Job summary

Korn Ferry is looking for an experienced backend engineer to design, develop, and maintain server-side APIs for large-scale mobile applications. You will work across teams to define scalable solutions and contribute to CI/CD pipelines while ensuring performance and reliability.

Requirements include strong Kotlin/ JVM language skills, REST and GraphQL API experience, and a solid background in asynchronous programming and testing. The role emphasizes code quality and collaboration.

Qualifications

• Proven experience building server-side applications with strong back-end practices.
• Proficient in Kotlin or related JVM languages.
• Experience with RESTful and GraphQL APIs.
• Hands-on experience with Gradle or similar build tools.
• Strong debugging and performance optimization skills.
• Experience with CI/CD pipelines and automated testing frameworks.

Responsibilities

• Design, develop, and maintain the mobile service layer (Backend-for-Frontend) for large-scale apps.
• Deliver secure, reliable server-side APIs for real-time consumer experiences.
• Write clean code and participate in reviews, refactoring, and continuous improvement.
• Collaborate with mobile, product, and design teams to define usable solutions.
• Troubleshoot and optimize performance for responsiveness and scalability.
• Create unit and integration tests to ensure reliability.
• Follow CI/CD practices and contribute to pipelines and build systems.
• Share ideas and participate in solution design discussions.

Skills

Kotlin

Java

Scala

REST API

GraphQL

Gradle

Async programming

CI/CD

Testing

Distributed systems

Performance

Debugging

Tools

Docker

Kubernetes

Job description

• 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 discussionsProven 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)