A Mobile iOS developer designs and builds applications for Apple devices using programming languages such as Swift or Objective-C. They work through the entire app development cycle, from concept and design to testing, debugging, and deployment to the App Store. They ensure the performance, quality, and responsiveness of applications, collaborate with cross-functional teams to define app features, and identify and fix app bottlenecks and bugs. They also follow Apple's design principles and interface guidelines. Moreover, they may need to integrate apps with backend services and maintain the code and atomization scripts for robustness, usability, and reliability.