[haidrali]

As far as I know google has standard procedure for hiring software engineers regardless of of front end or backend, phone screenings followed by on-site interviews. You are supposed to have good data structure and algorithmic knowledge. I would suggest to go with data structure and algorithms, also System Design is very important and your past projects ( if you are experienced one ). Try to get as much information as possible from your recruiter about your interview that will surely help.

Best of luck for the interview.