A telephonic interview is the first step in the interview process. It is a straightforward Data Science Q&A session. An onsite interview follows the phone interview. Interviews with team heads, team members, and SVPs are part of the onsite interview. Before the onsite, there may or may not be an online SQL assessment. SQL evaluations are pretty tough. Citigroup's data science team works using Hadoop and Spark. Their questions cover a wide range of topics, including coding, SQL, Systems Design, Hadoop, and Spark. They are based on both fundamental and advanced Data Science concepts. If you work hard on your fundamentals, you will almost certainly get hired by one of the world's largest banks!