A lot of red flags here.
The person that interviewed me was very rude. They start by telling you that they've only ever hired one senior engineer in the entire history of C3. Then they tell you that only 1% of applicants get the job. I don't know who told them that's a good way to generate interest in their job vacancies.
And then the biggest red flag: this person got angry when I asked about the perks. Basically after that, she wanted to end the call as quickly as possible and didn't even want to explain the interview process. I would never work for a company like that.