Historically speaking, the iOS UK app was running on Bitrise because it was decided not to invest time in implementing a CI solution, while the Bristol team was using a Jenkins version installed by a different team. Only one team member had good knowledge of Jenkins but the rest of the team showed little interest in learning how to configure and maintain it, causing the stack to eventually become a dumping ground of poorly configured jobs. JCasC stands for Jenkins Configuration as Code, and it allows you to configure Jenkins via a yaml file.