StackAdapt Machine Learning Engineer interview questions

First it was the screening call with recruiter with just comp expectations and thoughts about the role First round of interview: Chat with lead engineer. Then 2 high level technical questions, no coding just explaining how I would solve the question. very basic questions (how to use hashmap, queues, LRU..) Second Round: 1-hour interview with senior engineer. One question was leetcode+stats and probability, another one was an Spark+Big data question which I couldn't answer