I had a technical and introduction round with the Hungarian. Another round with the team lead based in San Francisco and another round which was a sort of culture fit round and the manager wanted to make sure that I understand the role fully. The questions were not particularly hard.

Received a call from a recruiter, first interview was scheduled. First and second round are technical in nature. 1st Round was around only project details and Scala programming language. Every answer was followed up by a in depth discussion. One coding problem. 2nd Round - Spark Technical. Two practical questions, one where you needed to point out where the code will run(driver/executor) on RDD. Second was a DF problem. Less theory more practical. 3RD round - Manager. This depends on who is taking your interview. Be confident and clearly explain what is your role in current project/company. Why you want to join BlackRock. They might ask you some puzzle questions also.