I applied through linkedin and received an assignment to make an iOS app. After spending few days on it and submitting the app, I received an email that they have given an offer to someone. I think it would have been better if there was some communication before sending the take home assignment which could have shown the seriousness for job interview.

The interview process is pretty normal and not very long. First HR interview, then a technical interview with two of the people from the iOS team (one lead developer and one non-lead); if you pass this stage then they will give you an assignment, after you send the assignment, they evaluate it; and if they accept it the recruiter will contact you and make you an offer.