在google appengine(python)中存储配置的好地方是什么?

class Configuration(db.Model):
  _INSTANCE = None

  @classmethod
  def get_instance(cls):
    if not cls._INSTANCE:
      cls._INSTANCE = cls.get_or_insert('config')
    return cls._INSTANCE

class Configuration(db.Model):
  CACHE_TIME = datetime.timedelta(minutes=5)

  _INSTANCE = None
  _INSTANCE_AGE = None

  @classmethod
  def get_instance(cls):
    now = datetime.datetime.now()
    if not cls._INSTANCE or cls._INSTANCE_AGE + cls.CACHE_TIME < now:
      cls._INSTANCE = cls.get_or_insert('config')
      cls._INSTANCE_AGE = now
    return cls._INSTANCE

config.py

AMAZON_KEY = 'XXXX'

import config
service = my_amazon_service(config.AMAZON_KEY)

from google.appengine.ext import ndb

class Settings(ndb.Model):
  name = ndb.StringProperty()
  value = ndb.StringProperty()

  @staticmethod
  def get(name):
    NOT_SET_VALUE = "NOT SET"
    retval = Settings.query(Settings.name == name).get()
    if not retval:
      retval = Settings()
      retval.name = name
      retval.value = NOT_SET_VALUE
      retval.put()
    if retval.value == NOT_SET_VALUE:
      raise Exception(('Setting %s not found in the database. A placeholder ' +
        'record has been created. Go to the Developers Console for your app ' +
        'in App Engine, look up the Settings record with name=%s and enter ' +
        'its value in that record\'s value field.') % (name, name))
    return retval.value

AMAZON_KEY = Settings.get('AMAZON_KEY')