Close this store and release any resources.
Close this store and release any resources. It is undefined what happens on get/multiGet after close
If a key is present and successful in the cache, use the cache value.
If a key is present and successful in the cache, use the cache value. Otherwise (in a missing cache value or failed future), refresh the cache from the store.
Get a set of keys from the store.
Get a set of keys from the store. Important: all keys in the input set are in the resulting map. If the store fails to return a value for a given key, that should be represented by a Future.exception.