my_config.rb

#    t.string   "key"
#    t.string   "val"
class MyConfig < ActiveRecord::Base

  class << self
    def all_as_hash
      begin
        Rails.cache.fetch(:my_config_hash) do
          h = {}
          all.each { |m| h[m.key] = m.val }
          h
        end
      rescue
        {}
      end
    end
  end

  after_save do
    Rails.cache.delete(:my_config_hash)
  end

end