If you have a use case that doesn't fit into your basic CRUD why not just create a new REST resource for it? For instance in my current app we have an InstallsC

If you have a use case that doesn't fit into your basic CRUD why not just create a new REST resource for it? For instance in my current app we have an InstallsController. This creates a new installation of the plugin, updates the user's account and send out an email. I've always steered clear of model callbacks as they don't play well with FactoryGirl/Machinist etc. As such the controller's create action describes everything that happens when our plugin is installed(it's still only 4 lines long). This strategy of using new REST resources combined with modules for models where appropriate seems a very comfortable way to structure a large application. It fits into the rails conventions well and doesn't require new developers to do anything they're not familiar with. The other nice advantage is that your routes configuration gives a great overview of everything that can happen in your app.