Interface CachingStrategy

Cleans up any expired cache values

Deletes the key from the cache

Returns the expiration time, or undefined if it doesn't exist

Returns the cached value, or undefined if it doesn't exist

Sets the value in the cache, with an optional expiration (as a future Game.time)

Wraps the cache in a serializer to store objects more compactly. HeapCache notably needs no serializers and simply ignores this.