For me the interview had 3 stages.
First stage was meeting the CTO and having a nice chat, asking about my experience.
Second one was meeting both CEOs and having a nice chat, they've asked me a few questions about how I would develop certain things, some trick questions etc.
One interesting point to make is that: I didn't know one question, I was honest that "I don't know that honestly" and that was it. So don't be afraid of admitting you don't know.
The final stage was a small demo to show off my skills. I had a week to finish a certain task and that was the final thing to do. I finished it within 2 days and got my offer sent to my inbox on the third day. So they're moving fast, I liked it.
Interesting point: Both founders are programmers, so you can go full-on programming talk with them during interviews.
