Waste, Waste and Waste.
part-1
Its a complete waste of your time. HRs are pretty immature. After 2 rounds, which went pretty good, they suddenly asked for salary details and expectation. 3 interviews were pending but after just 1 additional interview, all the remaining interview got cancelled. I quickly called HR, she got nervous, she said 1 round didnt go very well, the head HR would contact for details and cut the call. I didnt receive any call after that.
All the interviews went pretty good, interviewers themselves said that they are satisfied with solution.
I am sure that they realised that they cannot give hike or cannt meet expectation. They are just mass interviewing people without looking at their current salary and expectation. That would result in waste of you precious time.
part-2
you may be surprised to see that 2-4 years experience guys are taking 15 years exp guy interviews. Interviewers are theoretically & technically good but they lack some of system design aspects because they have not seen or face real production design issues and dont have real exp of seeing/doing much of design work. They are immature in that. So stick to basic theoretical design if you want to make them happy ( thats what i did :) )