Initially started with a phone call speaking with the Big Data Architect and (if I recall correctly) a Senior Product Owner. They asked about my background and what I thought Volo did. Then they asked a few technical questions to check my CV and background a bit. The phone interview was successful and I was asked back for a face-to-face interview at their offices.
I arrived for the face-to-face interview and was shown around their offices (which are impressive - the full top floor of an office in the middle of Cheltenham with floor to ceiling windows all the way around, very cool). I met with the Big Data Architect and the Data Scientist. They quizzed me about my background and we spoke about their platform. They asked me to draw a diagram of how the data would flow around the system. Then they asked a couple of logic-based questions.
We had a break, they gave me some food, and then had a relatively quick soft skills interview.
I heard back a few days later that my application was unsuccessful. I received quite detailed feedback through the recruiter (for example I had given up too easily on one of the logic based questions), and that I didn't have enough prior experience. I was grateful for the detailed feedback and it was accurate and fair. The only negative point was they were aware of my experience level from my CV, the recruiter, and the initial telephone interview, so it was a bit odd to get that as feedback from the final stage. Otherwise it was a good process, very friendly and clearly knowledgeable people and it was a good experience being able to talk to them and they were very happy to answer my numerous questions!