I applied online and got a reply over email from the CEO, asking to do a 2-4 hours coding challenge. This is before interview or a phone conversation. Usually I am more careful before I spend time, but it's COVID time and I needed a job so I agreed. It was a sorting problem of a table with some custom rules. I used Python's built-in sorted() function with a custom comparator, that has a worst case compleity of O(nlogn), and tested on the sample input. Pandas probably would have been better, but the question asked to not use any 3rd party libraries. I got a reply a couple of days later that the engineering team was not impressed. Fair enough, I thanked them for the opportunity and asked how could it be done better. I received no reply. Usually in coding challenges the interviewer explains if there is a better algorighm to solve a problem. I looked at the company at LinkedIn and seems it has very few employees. The CTO is pretty young who has a bachelor's degree and only a couple of years of experience before becoming CTO. Usually such high positions require 10 - 20 years of solid industry experience. I checked the github account, it's a bunch of forked repositories. Based on what I saw, I could not tell if the company is real or profitable or has good engineers or products. It probably was for the best to not have spent more time.