Deployment of RadarrAPI is done manually to https://radarr.aeonlucid.com/ by @AeonLucid.
This is the services API of https://github.com/Radarr/Radarr. The API is created from scratch and not based on Sonarr because it's not open-source.
The most important task of this API is to provide auto-updating to Radarr.
If you want to work on RadarrAPI, make sure you have .NET Core installed.