Senior Mobile Developer – Global Market Research Organisation - 6 month contract OverviewI am currently recruiting for a Senior Mobile Developer with strong expertise in Native iOS (Swift) and Android (Kotlin) to join my client who are a Global Market Research Organisation.The organisation operates a large-scale passive measurement platform across European and APAC markets, combining technologies such as audio content recognition (ACR), location tracking, and survey research to measure real-world media exposure and advertising effectiveness for enterprise clients.Its consumer platform with continued expansion planned across both Europe and Asia. The mobile platform runs on both iOS and Android and operates in production across multiple markets, meaning your engineering decisions will have a direct impact on real users.Role ResponsibilitiesDesign, build, and maintain native mobile applications across both iOS (Swift) and Android (Kotlin) platforms.Develop and maintain the core native infrastructure layer supporting passive measurement technologies such as background processing, audio recognition, and location tracking.Ensure reliable background execution and efficient battery usage while handling continuous data collection on user devices.Integrate mobile applications with backend services using secure and efficient API communication.Work closely with backend engineers to ensure efficient data exchange, synchronization, and processing pipelines.Implement and maintain mobile CI/CD pipelines, automated testing, and app store deployment workflows.Monitor and diagnose production issues using debugging, profiling, and observability tools.Ensure applications comply with privacy regulations and platform-specific policies across multiple international markets.Essential Skills and ExperienceStrong professional experience developing native mobile applications in both Swift (iOS) and Kotlin (Android).Proven track record delivering production-grade applications on both platforms.Deep understanding of platform-specific lifecycle management, background execution models, and permission handling on both iOS and Android.Experience integrating RESTful APIs, including authentication mechanisms such as OAuth or JWT.Proficiency with native debugging and profiling tools, including Xcode Instruments and Android Studio Profiler.Hands-on experience implementing and maintaining mobile CI/CD pipelines using tools such as Fastlane, GitHub Actions, or Bitrise.Experience managing mobile application releases and deployment workflows for both major app stores.Ability to troubleshoot complex performance issues including battery consumption, memory usage, and background task reliability.Desirable Skills and ExperienceExperience working with native audio processing, sensor APIs, or hardware-level integrations.Familiarity with cloud infrastructure environments (particularly AWS).PackageInitial 6 month contract (possibility of extension)Competitive and flexible rate dependent on level of experienceExcellent benefitsHybrid (3x week in Groningen)