Senior Mobile Developer (iOS/Android) - SDK & Platform (all genders)

• Design and develop SDK components and modules for iOS and Android that partners and customers use as building blocks for their own apps
• Define and evolve clean, well-documented public APIs for our SDK, balancing flexibility for partners with simplicity and consistency
• Contribute to and help shape our entire frontend stack, including cross-platform and web technologies
• Work with the native iOS SDK / Android SDK and programming in Swift/Kotlin (Objective-C/Java legacy knowledge a plus)
• Continuously evaluate new technologies, prototype them, and assess their fit for our SDK architecture
• Ensure quality and stability through automated tests, code reviews, and strong engineering practices, treating the SDK as a product partners depend on
• Proactively identify gaps, edge cases, and improvement opportunities rather than waiting to be told what to build
• Collaborate closely in an agile, cross-functional team, taking ownership of technical decisions and contributing ideas beyond your immediate task

• Completed studies in computer science or equivalent qualification, with several years of hands-on experience in Swift and/or Kotlin (Objective-C/Java experience welcome)
• Proven experience building or maintaining an SDK, library, or platform consumed by external developers or partner teams
• You understand API design, versioning, backward compatibility, and developer experience
• Strong know-how in client-server communication, databases, and web services
• Very good knowledge of iOS/Android standard frameworks, APIs, and common design patterns
• A quality-first mindset: comfortable writing automated tests, reviewing code critically, and pushing back on shortcuts that hurt long-term maintainability
• Demonstrated ability to work iteratively and proactively
• Conversational English; German skills advantageous
• Enjoy working in motivated, international, cross-functional teams and mentoring or collaborating closely with partner developers

At GK - a global leader in retail technology and part of the Fujitsu Group, specializing in checkout, store operations, and customer experience - you're not here to maintain the status quo - you're here to disrupt, innovate, and elevate., Why Join GK? * Mission-driven: We simplify interactions in retail - for businesses and customers alike. * Empowered by flexibility: Remote-first, flexible hours - work where and how you thrive. * Security with vision: Permanent contract in a future-focused, stable environment. * Culture that connects: Open, collaborative, and people-first - with great coffee if you drop by . * Backed by strength: With 35+ years of retail tech expertise and as part of Fujitsu, a global IT leader. * Tech that scales: AI-powered solutions built to grow with the world's leading retailers. * Think global: 570,000+ installations in 65+ countries. Real impact, worldwide.