Octopus Energy Backend Developer interview questions

I interviewed for the Kraken Technologies arm of Octopus Energy The interview process consisted of: - a short preliminary call with someone from the internal recruitment team which was a mix of a culture check and an opportunity for me to find out more about the team and company - an interview with 3 members of the larger Kraken team talking about relevant experience and knowledge - a take home technical challenge (3-4 hours long) - a final technical interview discussing the challenge and other related technical questions with members of the hiring team