Good points this wasn't entirely a protobuf-specific issue, so much as it was a (likely hierarchical and historical set of) bad decisions to use it at all.

Using Protobuffers for a few KB of metadata, when the photo library otherwise is taking multiple GB of data, is just pennywise pound foolish.

Of course, even my preference for a simple JSON string would be problematic: data in a database really should be stored properly normalized to a separate table and fields.

My guess is that protobuffers did play a role here in causing this poor design. I imagine this scenario:

- Photos.app wants to look up location data

- the server returns structured data in a ProtoBuffer

- there's no easy or reasonable way to map a protobuf to database fields (one point of TFA)

- Surrender! just store the binary blob in SQLITE and let the next poor sod deal with it

You have to take into account the fact that iPhoto app has had many iterations. The binary plist stuff is very likely the native NSArchive "object archiving (serialization)" that is done by Obj-C libraries. They probably started using protobuf at some point later after iCloud. I suspect the unicode crap you are facing may even predate Cocoaization of the app (they probably used Carbon API).

So it would make it a set of historical decisions, but I am not convinced they are necessarily bad decisions given the constraints. Each layer is likely responsible for handing edge cases in the application that you and I are not privy to.