Devise is Rack based, a MVC solution based on Rails engines, allows one to have multiple roles (or models/scopes) signed at the same time, based on a modularity concept. It is composed of 12 modules: Database Authenticable, Token Authenticable, Omniauthable, Confirmable, Recoverable, Registerable, Rememberable, Trackable, Timeoutable, Validatable and Lockable. There are a number of extensions to be found at the github homepage of devise.