Explore runtime modes and plugins in Erlang through this conference talk from Code BEAM Europe 2022. Dive into Ulf Wiger's experience implementing `app_ctrl` and `setup` in the Aeternity Core blockchain system, drawing inspiration from the Ericsson AXD 301 system. Learn about core OTP principles, key features, and innovative techniques for adding new functionality to stable systems. Discover the progression from early AXD 301 days to modern blockchain applications, covering topics such as Runtime Configuration Manager, sysInstall, app_ctrl implementation, and plugin configuration. Gain insights into Erlang development and architecture, suitable for developers and architects looking to enhance their understanding of OTP and system configuration in mature projects.