Open Radar

 
I work on Moovit for iOS, a global free transit data app.

The bug isn't very consistent in its occurrence but we have received numerous complaints about it. 
Users report that merely opening our app causes the entire device to become unresponsive, including the Home Screen, App Switcher, other apps and our application, of course. 

The issue isn't specific to old or new devices but appears to occur on iOS 12.2 - 12.3.1. 

This is anecdotal, however, since no actual crash occurs therefore we have no way to gather statistical data.
We have determined that the issue does stem from Spotlight indexing. We did this by turning the index operation off and shipping a test build to affected users. The code in question cannot be revealed, but what it does is index several thousand items into CSSearchableIndex.default. I have found no indication that this is prohibited or not recommended.

I'm sorry that I can't provide a specific reproduction scenarion. I did manage to get a sysdiagnose from a user shortly after they experienced the issue.