Minimize key size by storing as binary array

To reduce overall memory consumption, and make most efficient use of resources, the client should be able to store data as a binary array instead of in a string representation. For example, a GUID which might take 36 bytes as a string can be stored as a 20-byte binary array.

However, the .NET client API doesn't provide any means to store non-string representations of keys, so we're not able to maximize efficiency in this way.