active_model_serializers

I came here to say the exact same thing. After having worked on/scaled an API that served >100k requests per minute, I feel I can say with some experience that defining your JSON in your model is a very bad idea. A classic example that we ran into repeatedly: Assume you want to have an endpoint that populates a user's profile (for the user to see). You probably want id, name, email, age, location, created_at, updated_at, etc. However, when exposing this same user instance through an endpoint that publicly aggregates users (e.g. search), sending over all those fields is 1) overkill, and 2) raises privacy concerns. So far, my favorite approach to this problem uses the ActiveModel::Serializer gem (https://github.com/rails-api/active_model_serializers). It moves the JSON logic to something more akin to a view, and provides an easy way to p

Rails-api is a gem that configures rails in a more lean and mean fashion for API usage, it doesn't handle the json serialization. Mostly rails-api disables a lot of default rails features/middlewares that aren't needed when you're only building an API. For json serialization you may want to look at Active Model Serializers[0], I found it much easier to work with than rabl, and it's also written by the rails-api group. [0] https://github.com/rails-api/active_model_serializers