Crossover for Work interview questions

Hiring consist of 8 online test. I cleared all the rounds of online test and I was emailed that your application is rejected and I was not even told the reason of the same . Even though I cleared all the rounds. They are just wasting the time of candidates. So its better not to apply to crossover. Its a complete wastage

I have to do a very complex excercise which involved coding a very complex program using MongoDB. I had to complete everything in a couple of hours and under pressure.