Codility has simple questions, but you need to know a math trick. After that, you will have a round with the team you want to join, so it's a lottery. Overall, it's not that hard if you have experience or are well-prepared.
Leetcode easy/medium questions: arrays.
The following metrics were computed from 59 interview experiences for the Rakuten Software Engineer role in Japan.
Rakuten's interview process for their Software Engineer roles in Japan is fairly selective, failing a large portion of engineers who go through it.
Candidates reported having very good feelings for Rakuten's Software Engineer interview process in Japan.