I applied through an employee referral and the process took less than a week. I was contacted by HR a few days after the referral. The HR explained to me about the recruiting process. 1) Online coding exam, 2) 2 rounds of technical interview, 3) onsite. I passed the codility exam and was contacted by the team manager for first round of interview. The manager asked questions about my resume, how well do I know about python, C/Java and Pig. And then explained to me about the position. Generally speaking, I prepared a lot more than what he asked for, looked into the skill sets required by the job and read all the previous interview comments about the "data scientist" position. To my surprise, there wasn't technical stuffs at all. I felt like I did really well and the manager liked me. However, I received a rejection letter from Twitter a few days later. I think I got rejected based on my credential (Fresh out of college with a graduate degree in Stats) and not about my interview skills, since the data scientist position at Twitter is realllllly competitive. Overall, I felt like they interviewed me because they have to interview people from referrals regardless of what they think about the candidate. I'd rather not to spend 2 weeks of my time preparing for an interview if I knew they were like this. Since my knowledge on Hadoop/map-reduce were mostly from seminars, so I bought books from Amazon and dug into that.