Interview with founder first, and then a data challenge. The data challenge they ask you to code a random forest from scratch for no apparent reason. The paper they give you to implement doesn't actually change the internal structure nor require a rewrite for any reason. I strongly believe in not re-inventing the wheel not necessary. Also, there was an aire of we are smarter than you saying they could solve the problem and write an entire random forest class in 3 hours. I would love to see the scikit-learns decision tree and rf forest written in three hours, even by the main contributor. Then, you had to also write the additions from the paper which were pretty simple and produce standard metrics for the output. The additions of the paper external to the RF dealing with imbalanced classes and metrics were easy. That could be done in a few hours no problem. Anyways, that part just left a bad taste in my mouth. The founder did seem nice and motivated, so that was refreshing.
