I was contacted fairly quickly after applying online. I didn't find any of the interview questions very hard. What struck me was the type of questions: how-do-you-solve/do-xyz, where xyz is specific. Nowadays it seems any job involves data analysis is called data scientist. As a statistician, my job search 95% of the time led me to data scientist position postings. In the pre-data-science period, statistician interviewers were composed of at least half internal data customers from various domains. They wanted to know how I can help them achieve their research or business goals with data. In contrast, all of my data scientist interviewers (not just at Twitter) were younger and more computing savvy data analysts from quantitative background. They wanted to know if I know how to do xyz, where xyz is something they themselves have encountered. This difference is important for candidate and employers of data scientist.