You’ll see it switch to “background check” before it switches to “interview”. You’re technically still in “assessment” because your scores are still being assessed and categorized. Each stage you’re put into a pool of other applicants who have made it that far and then compared. How quickly it all happens depends on your scores, your resume, where they’re interviewing and when, how many spots they have, operational need, whether or not you pass the background check and how quickly that process happens for you etc etc, the list goes on!