An interview process is fast and streamlined.
It is 30 minute recruiter call with general discussion of your experience and motivation.
If you pass - then you are scheduled a so called Mini-Case for 1 hours and provided a couple of helpful materials to prepare. The case will be based on one of a several C1 products - like shopping app, mobile app for cards and accounts or loans. You will need to understand the problem, check some emails and prototypes and suggest changes. Then you are presented some data to analyse and do some basic calculation on the metrics - e.g. what is more profitable A or B and why. The interviewer is collaborative and the communication was good.
If you pass - you are scheduled a so called Power Day. You are also provided examples and even some additional consulting cases to prepare. The Power Day is 4 1-hour interviews: product skills, two product cases, product discovery. You will have 30 minute break in between and if some will end sooner - probably will be able to use the bathroom, if you are lucky.
I didn't pass this round so my impression may be biased but hear me out.
The product skills is focused on one product you worked on from inception to go-to-market. My interviewer was late but it went good from there. In my humble opinion, this one is the best of all as you discuss the case you know, you know user problems, your business impact, your metrics etc and need just to present it clearly to your interviewer. They will also guide you through it asking questions. It was an interesting talk. We didn't have any spare time and the next interviewer joined right away. I was trying to avoid drinking water.
Then you have a product case, it is a consulting-like case with some simple enough math. A derailed a couple of times in my calculations - didn't recognise weighted averages right away but the interviewer was really helpful and gave hints.
Then you have your 30 minutes break where you need to fit everything including taking a break.
The next one was again a product case. Not sure why C1 decided to have two of these cases? They are pretty similar and my second one was even more easy. At this point you feel you are getting tired.
The last one was a product discovery, with an example of improving DMV. This one I didn't appreciate at all. Not sure what is the value to work on this abstract case when you just presented your real product. Then at this point I was really tired. I won't be tired at a normal working day as I'm taking breaks and the stress level is much less. The interviewer wasn't really helpful here explaining what you need to do. They gave really abstract guidance - e.g. think about everything here, and even made me doubt my problem statements and hypotheses (like it is some physics postulates and not hypotheses). This last one was disappointing experience and just too much for one day. I believe I failed because of this last one, as I just got tired at this point, got a sever cough from talking for 4 hours straight...
It either should be 3 interviews max, or split to two/2 days (2 hours and 2 hours) or maybe a series of 45-minute slots. Even to find 4,5 hours straight when you are employed can be quite tricky.
All-in-all you will need 6 hours and X h to prepare.