Summary: Join our dynamic Mobile Engineering team as a Senior Java Engineer to build the Backend for Frontend API layer for award-winning mobile applications serving millions. Highlights: 1. Play a key role in building the Backend for Frontend API layer 2. Collaborate with engineers, product managers, and designers 3. Design thoughtful and innovative solutions for open-ended challenges We are seeking a **Senior Java Engineer** to join our dynamic Mobile Engineering team, where you will play a key role in building the Backend for the Frontend API layer that powers award\-winning mobile applications serving millions of cardholders worldwide. This position offers a unique opportunity to collaborate with engineers, product managers, and designers to craft interactive experiences throughout the consumer journey. **Responsibilities** * Build server\-side applications for scalable and high\-traffic systems * Write, refactor, and optimize clean, maintainable code * Facilitate performance analysis and optimization to ensure robust systems * Collaborate with the team to fix bugs and enhance legacy code * Integrate bespoke backend services to extend functionality for modern applications * Design thoughtful and innovative solutions for open\-ended challenges * Contribute to continuous integration processes using advanced build tools * Ensure robust application quality through comprehensive unit tests * Advocate for open source contributions to help drive innovation * Share ideas and insights to improve user experience and application design **Requirements** * Degree in Computer Science, a related field, or equivalent practical experience * 3\+ years of experience crafting server\-side applications with a focus on performance and optimization * Expertise in Kotlin, REST, and GQL, alongside familiarity with Gradle and RAML * Proficiency in asynchronous code and deep understanding of modern architectures * Background in writing, refactoring, and deleting code aligned with industry best practices * Capability to navigate and enhance legacy systems while integrating modern solutions * Experience with unit testing and continuous integration tools * Fluent communication skills in English at a B2\+ level **Nice to have** * Experience of working with open source projects * Familiarity with bespoke backend services from legacy systems * Background in designing creative solutions for undefined technical problems