Paste this into the rails console and see the total number of callbacks your application has defined for its models.

puts_callbacks.rb

Rails.application.eager_load!

models    = ActiveRecord::Base.descendants.map(&:name)
callbacks = []
callback_types = %w{ _save_callbacks _create_callbacks _destroy_callbacks _validation_callbacks _commit_callbacks }

callback_types.each do |callback_type|
  models.each do |model|
   callbacks << instance_eval(model).send(callback_type)
  end;nil
end;nil

puts "#{callbacks.flatten.count} total callbacks"

It should make you feel gross.