I now use Core Data more often now. Here is how I usually use it, for example in Push Hero
From iOS 10 and macOS 10.12, NSPersistentContainer that simplifies Core Data setup quite a lot. I usually use 1 NSPersistentContainer and its viewContext together with newBackgroundContext attached to that NSPersistentContainer
In Core Data, each context has a queue, except for viewContext using the DispatchQueue.main, and each NSManagedObject retrieved from 1 context is supposed to use within that context queue only, except for objectId property.
Although NSManagedObject subclasses from NSObject, it has a lot of other constraints that we need to be aware of. So it’s safe to treat Core Data as a cache layer, and use our own model on top of it. I usually perform operations on background context to avoid main thread blocking, and automaticallyMergesChangesFromParent handles merge changes automatically for us.