The process was composed of 4 meetings plus one technical challenge. The first meeting was merely an introduction that led to the technical challenge. This challenge took me a weekend and a night to fully solve. One needs to be comfortable with the company's technical stack to solve it successfully.
A few days after the technical challenge I was invited to a meeting with two engineers where we discussed the implementation, this meeting took almost 2 hours.
After that, I had another call with the CTO to get to know ourselves that took about one hour, and in the following day, I had another call with the CEO which took about thirty minutes.
Shortly after this, I received a proposal.