Core Data

For apps still on Core Data rather than SwiftData, this covers the full persistence stack: setting up NSPersistentContainer, threading rules with perform blocks, NSFetchedResultsController for table views, and batch operations that run at SQL level. It includes iOS 17+ features like staged migrations and composite attributes, plus persistent history tracking for multi-target sync. The concurrency section is solid on the "never pass NSManagedObject across threads" rule and shows how to use objectID with Swift concurrency. If you're maintaining a Core Data codebase or need features SwiftData doesn't expose yet, this has the patterns you actually use in production, not just CRUD basics.