Core Data has a popular opinion of being hard to use, especially in concurrent environments. Why is that the case? First, it truly is complex because it solves a hard problem. Second, until WWDC16 Apple haven't really said how to best set up the Core Data stack. There were many options, each with its own issues, that we had to choose from.That's why I'm super happy that things get clearer in iOS 10 with the introduction of NSPersistentContainer.