I was very interested in the job description. So I applied while I was in the Bay Area for a week.
They got back really fast, because they saw that I had mentioned in the cover letter about me being in town.
I had a phone screen first and then they scheduled an on-site interview. At the on-site interview, I met with their engineers who worked on the team I was interviewing for.
The process was clean, timely, and everybody was very involved - at no point did I feel that the engineers considered interviewing a chore.
Their genuine enthusiasm came through. They gave me time to ask questions, they were courteous and patient when asking questions, and they spoke about the work culture and the company business model in depth. They cared about the technical and personal fit of a candidate to the role and also with the company culture.
An interesting, unexpected experience was that they also had a non-interviewing engineer come in and talk to me at the end, so that I could ask him my questions without feeling tense.
I think it is important anywhere (and especially for start-ups) to write a cover letter with the application so that it highlights your motivation in applying to a position with them.
The questions I was asked were all related to the job I was applying to. There was a mix of CS questions (because it is a software position) and domain-specific questions (because it is a Machine Learning position). I signed a NDA, so I cannot talk about the questions.
-- It is different from larger companies interviews, where there are slots of 45 minutes for a single CS question or two, and where people might not have the time to talk about past experiences listed on your resume. Here, there is time to talk about things on your resume. So make sure that you are ready to talk about your research or school projects or past work!
-- The folks are laid back, so I'd say leave the suits at home.
-- The place is located in San Mateo off the 101. So if you are coming down from San Francisco or up from San Jose, I recommend some slack to be on time for the interview.