Change notification ResumeTokens are composed of the logical time timestamp, the fully qualified collection name, and the document key of the changed document. In the initial version, these three components will just be fields of a BSON object, and comparisons inside the server for relative ordering will use BSON's woCompare() function. If instead we keystring-encoded that document, then the ResumeTokens become truly opaque blobs which forces users and drivers not to rely on their current format or try to inspect them. It also could give us a performance win since now the internal comparisons the server must do to put notifications in order can be bytewise comparisons instead of needing woCompare().