Lotto24 - iOS

At Lotto24 AG, I worked as a Senior iOS Engineer, later leading the iOS technical direction and mentoring a team of six mobile engineers. My primary focus was to modernize a legacy Objective-C codebase into a clean, modular Swift architecture with a strong emphasis on reliability, accessibility, and performance. Over four years, I drove the platform transformation through modularization, testing automation, and continuous performance optimization. The app serves millions of lottery players in Germany, handling critical user flows such as ticket purchase, draw tracking, and wallet management—demanding high stability and compliance. Key Contributions: - Led the migration from legacy Objective-C to a modern Swift MVVM architecture, introducing SPM modularization and a pragmatic path toward SwiftUI adoption. - Introduced Core Data–backed offline-first workflows, enabling users to manage tickets and cart operations even without network connectivity. - Built and mentored a team of six engineers, running 1:1s, reviews, and growth sessions that strengthened code quality and delivery predictability. - Established Clean Architecture boundaries with clear dependency injection and DI container configuration for safer refactors. - Set up a full CI/CD pipeline using Fastlane and GitHub Actions, automating test gates, release validations, and deployment workflows. - Implemented a comprehensive testing strategy (unit, UI, snapshot) that increased coverage from ~30% to ~60% and reduced production bugs by 20%. - Improved app cold start time by ~25% through lazy initialization and removal of main-thread blocking tasks. - Introduced Lotto24 Widget-first design with full control, Dynamic Type, and contrast compliance, enhancing inclusivity. - Delivered watchOS features reaching 200K+ weekly users, driving engagement up by ~18%. - Reduced technical debt by ~70% through modular refactors and enforced API boundaries.