Quick, roll-your-own key-boolean caching

application.rb

module MyApplication
  class Application < Rails::Application
    config.cache_store = :memory_store, {:size => 4.megabytes}
  end
end

prime_settings_cache_initializer.rb

Setting.refresh if ActiveRecord::Base.connection.tables.include?('settings')

settings.rb

class Setting < ActiveRecord::Base
  attr_accessible :enabled, :name

  after_save :cache

  class << self
    def refresh
      Rails.cache.clear
      all.each(&:cache)
    end

    def [] name
      return Rails.cache.read(name) if Rails.cache.exist?(name)

      if setting = where(name: name).first
        setting.cache
        setting.enabled
      else
        false
      end
    end

  end

  def cache
    Rails.cache.write name, enabled
  end
end