When I tried to integrate iCloud with Core Data, it was one of the most painful coding sessions I've ever experienced. I never did get the edge cases to work,

When I tried to integrate iCloud with Core Data, it was one of the most painful coding sessions I've ever experienced. I never did get the edge cases to work, for example there was a part during init that decided whether to use local data or iCloud data that I never understood (that could have been due to the example I was working from). Conflict merging was a huge PITA so I ended up just appending both datas with a human readable separator and letting the user decide which to keep. Honestly the whole thing was so gloriously bad compared with something like Firebase that I completely understand why Apple deprecated it. The way it should have worked was as a virtual directory with a callback/event when users attempted to write data, allowing the app to accept, revise or reject the change. This could be done on either a first-come-first-served basis or consensus algorithm specified per-path. It could also be implemented as a nonblocking compare and swap (CAS) so that any contention would have to be decided live, and the user's event log would be stored locally and resume from the first conflict when the user reconnected to the internet. Unfortunately that requires a GUI working more like React that can update to reflect the current state (which most apps don't do properly, if at all). Behind the scenes, storage would work similarly to a database transaction log so it's always deterministic. Apple should have then provided a paid service like Parse for apps that really need to deal with those callbacks in real time. Instead it feels like they swept all these details under the rug (which is impossible) so I never really trusted what iCloud Core Data was doing. I'm actually shocked that Apple went to the trouble of implemented iCloud storage without iCloud processing, but I digress. P.S. Core Data is actually conceptually ok with its ORM and versioning. My gripes are with the needlessly complex way it interacted with iCloud.