The entire interview process took about 2 months. After the initial technical screening, I was informed about all the steps involved and I knew where I was in the process at all times. The interview steps were as follows, with the times given to complete each step.
1. Technical screening (48 hrs)
2. Video describing role and larger technical assignment (1 hr)
3. Take-home assignment (1 wk)
4. Three rounds of follow-up questions about assignment (48 hrs for each round)
5. HR interview (30 min)
6. Interviews with other team members (2.5-3 hrs)
7. Reference check
The process did require a lot of time, but also provided the opportunity for both me and the employer to feel each other out and get an understanding of whether it would be a good fit. There was a great deal of transparency, responses were timely, and I felt prepared for what was expected at each stage.
The take-home assignment involved interpreting and explaining trends in historical data, with a bit for forecasting too. Whatever software or language you wanted to use for this assignment was fine, and the emphasis was on having strong justifications for each decision made. The follow-up questions dug deeper into the reasons for certain responses and evaluated the ability to communicate to different audiences. Problem solving, pattern discovery and interpretation were the main skills evaluated.
The HR and longer interviews were all with 1 or 2 other team members. These mostly focused on behavioral type questions to evaluate fit. There was a longer technical interview that went over answers to the take home assignment, and also involved some brain teasers to check abstract reasoning. Nothing crazy hard, but I did have to evaluate and interpret new material on the spot. Again, the main emphasis was on being able to reason abstractly and communicate clearly. Everyone I spoke with was considerate, engaged, and asked meaningful questions.
The downside to this process was the length. It did get stressful towards the end because I already had so much time invested. The company does place a high value on ownership and trust, and provides 2 months of training. Given this, I understand why evaluating each candidate very thoroughly is important. If you are not sure about whether you really want to do this job, the interview is not worth it.