My interview process was long, consisted of several calls with HR, one call with hiring manager an one call with a high director, as well as a phone skill screening with an engineer. I was then invited onsite, and had a long day that first featured a presentation about myself, then two technical interviews where I got to solve given problems on a whiteboard, then a social interview/lunch with various people from the company. After that I was asked to hold a presentation and teach their team something. And then a design interview as well as a concluding social interview with hiring manager. Everyone was really friendly yet professional and they paid for trip and hotel. The campus was nice. I did not get hired, but they gave me good feedback and asked me to apply again.

After a short sanity interview with their HR department I had a fairly easy technical screen focusing on my core C++ skills and basic design. This was followed up with a second phone screen with a Senior Engineer that delved a lot deeper and was more challenging. This interview went through knowledge of programmer practice, code, design patterns, etc. Passing this led to a full day in person interview, which was a series of talks mostly with people in the same department on the relevant skills (lots of white board problems) but with a significant set of interviews with people from other departments. The culture at Riot was obviously that of a young company, with lots of jokes but clearly everyone got along quite well. The technical interview was quite challenging, and went into large depth of low level knowledge as well as big picture design; it was easily the most challenging technical interview i've had in person, but never felt like a barrage of trivia questions and when I didn't know the answer was encouraged to take a stab at figuring out how I might do it.