Block Data Scientist Interview Questions
& Process

I did an online assessment that took 70 minutes. Then there were 3 rounds of technical screens. The first round was entirely algorithm-based. They had a very fast interview process; I got invited to the next round interviews the same night after finishing the previous ones.

First, I had an HR interview where we discussed salary expectations and they asked a quick SQL question. Then, the hiring manager interviewed me, asking about past projects and why I'm interested in Square. Next was a machine learning interview with a data scientist. I had to fit a quick ML model on my own computer to a dataset and discuss model metrics. Following that, a data manipulation interview with two data scientists, where I processed a dataset on my own computer. Then, an A/B testing interview with a data scientist, where I had to explain my thought process on running an A/B test. After that, a business interview with a stakeholder, where I explained my thought process on running a project with them. Finally, a last interview with the hiring manager where they asked how I deal with conflict. The HR rep and hiring manager were hostile/aggressive which threw me off.

This was the longest interview process ever. It began with a recruiter screening where I was asked two basic technical questions about finding unique values in a dataframe and what a window function is. Then, there was a technical round that included a 30-minute SQL interview covering basic SQL functions and a 45-minute Python interview focusing on string, tuple, and dictionary manipulation using for loops, all fairly standard stuff. Next, I met with the hiring manager for behavioral questions and to learn more about the role. The process culminated in an on-site day with 6 interviews over 4.5 hours. This included 3 technical interviews: the first, an hour-long data exploration session which felt out of place and poorly executed as I couldn't explore the data myself and the interviewer's requests were unclear, possibly due to inexperience. The second technical interview involved building a model from scratch, from preprocessing to evaluation, which was manageable with prior preparation. The third was a 30-minute A/B testing case study, which was straightforward. Finally, I had two more behavioral interviews and a second meeting with the hiring manager. One behavioral interview was particularly disappointing as the interviewer seemed disengaged and asked nonsensical questions.