I applied online and submitted an open source contribution to their GitHub. got a phone interview a couple of days later. That went pretty well, I submitted another open source contribution and a separate small assignment. After that I got an in-person interview with the lead engineer, co-founder, and a couple of department heads.
I thought the lead engineer did a really good job of assessing my skill level, best out of all of the companies I've interviewed with so far. He was patient, knowledgeable, willing to answer my questions in detail, and interested in putting in the time to properly assess candidates.
I'm looking for a first job out of bootcamp. I haven't confirmed with them, but think it's a safe assumption that they were looking for someone with more experience who could speak more fluidly on general coding/engineering stuff.
Regardless, it was good experience. Everyone I spoke to was very talented, warm, and had good energy. I think the company's going to do very well and I'd highly recommend applying.