If you are not satisfied with default to_json implementation of ActiveRecord. Here is the way out.

rails-how-to-customize-json

Customizing a model object's JSON representation, first of all, is a business of ActiveRecord::Serialization. You will look at ActiveModel::Serializers::JSON class


https://github.com/rails/rails/blob/master/activemodel/lib/active_model/serializers/json.rb

and then will come back to ActiveModel::Serialization class

https://github.com/rails/rails/blob/master/activemodel/lib/active_model/serialization.rb


- Non-subclassing approach

configure as/to_json method such options of :only , :except: , and :include 

- subclassing approach

You need to override (re-define) as_json method of your model class. 

for any specific key/attribute, you can def read_attribute_for_serialization method