The recruiter was very professional and quickly answered all the emails.
The interview process was as described in Deliveroo's website. All the technical interviews are with one person which raise some doubts regarding bias. The interviewer was looking for specific answers, yet he/she tells you there is no right answer. But as I can see in the feedback sent to me, the person was looking for very specific answers in most of the questions.
Different people accompanied the main interviewer in the interviews. Everyone were friendly.
After all round of interviews, they send you feedback, which is potentially a positive thing. But clearly they don't know how to give feedback, as it is all negative! They barely have any single good thing to say about you. To me, it is a very bad signal. Not many would want to work in such a culture.
The company claims that they value the diversity, but it is not true, at least not for this team. My background is in CS and not OR, and the whole feedback does not mention one single thing which shows they even considered that. Most of the feedback is actually about the miscommunications between two fields and the fact that the interviewers wanted me to talk completely OR. The most strange part is that they were not happy about clarification questions I asked, or the fact that I had to take some time to think before answering questions which were out of my main expertise.
Overall, it was an experience from which I learnt a lot. Every interview gives you some experience, which will be helpful later, hopefully to get a position which is a good fit.