X Data Science interview questions

I was introduced by a former employee and had a very long interview process. I had an online coding interview which was pretty easy. After that I had one coding and one data science interview. Then came the on-site interview which was two back-to-back data science/coding interviews on Skype. The process took so long (about 2 months since the first contact) that they told me that there are no positions left in Data Science team but they introduced me to Data Visualization team. I had 3 interviews with Data Visualization teams. In overall, while the interview process was frustrating, all the interviews that I had was great source of learning. So many interesting people are working on Twitter and it'd be nice to get a chance to work along them.