I applied through another source. The process took 2 weeks.

Waste of time - you would be much better off spending it with a reasonable company. These guys seem to be super confused as to who or what type of person they are trying to hire. Sigma contacted me online with a Senior Frontend/Full Stack position. After an initial "get to know you" phone chat, they sent me a HackerRank test that I thought was outright crazy. The challenge was titled "Frontend Engineer" and consisted of three questions - the first two somewhat reasonable, and the third one some crazy Dynamic Programming problem with lots of blinds and smoke and mirrors to obscure the problem statement. SERIOUSLY? In my entire life, I have not seen or heard of a single case when a frontend engineer would need to use DP - obviously, Sigma felt it is more important to have a CS whiz kid than a person who actually knows how to do the job they are hiring for. At any rate, I finished the challenge and sent it back to Sigma.

In a couple of days they scheduled another online "technical screening", this time the CoderPad type with a live person. That screening was even worse - imagine literally a "wall of text" for a problem statement and having half an hour to finish. Personally, I like to think first before I start coding, but here that was not the case. In the end, my code was working but not handling all the edge cases perfectly. I stayed up until 2 AM that night to finish the assignment and sent it back. The next day they told me "they decided to pass on my candidacy". My suggestion to Sigma: clear up your head first, figure out who you are trying to hire, and don't waste people's time with wild goose chases.

The DP problem was basically calculating longest palindromic sequences on substrings of a very long string.