The import status id backdating algorithm was the most difficult part of IG import.
It supports up to 999,999 users and is properly ordered by date (and random id that is incr by day and rolls over to the next day with leap year support, that was fun)
If @pixelfed ever needs to support more than 1 million users, I'll need to revisit the algorithm 😅
https://github.com/pixelfed/pixelfed/blob/dev/app/Services/ImportService.php#L12-L58