user.rb

class User < ActiveRecord::Base
  COLUMNS_TO_EXCLUDE_FROM_CACHING = ["id", "updated_at", "created_at", "last_request_at"].freeze
  COLUMNS_FOR_CACHING = (User.column_names - COLUMNS_TO_EXCLUDE_FROM_CACHING).freeze
  before_validation do
    unless (COLUMNS_FOR_CACHING & changed).empty?
      self.user_updated_at = Time.now
    end
    true
  end
end