In my didFinishLaunchingWithOptions method I spawn a thread to perform some maintenance on my core data store. However, this increases the startup time by half a second. The startup view is a tableview which draws its content from the same store. If I let the thread sleep for a second, the startup time improves drastically.

I would like to understand why the second thread is blocking/delaying the main thread. Is it because both are trying to access the store (The second thread has its own store coordinator and context) or another reason (e.g. dont spawn threads in didFinishLaunching)?