One bit of advice though, don't just jump into a mock, make sure you prep by studying first for a few weeks.
Once I realized the interviews were done by real people, I realized that would be the case. I was looking around to see if that was something that could be done on their site. It looks like it isn't but I found the following in their FAQ [0].
>If you need a place to start, we heartily recommend Interview Cake [1]. There, you can work algorithmic problems at your own pace and get nice hints as you go.
I wanted to post it here for anyone else wondering the same.
[0] https://interviewing.io/faq [1] I don't want to put the link here but the link from their FAQ does appear to be a referral link, or at least some kind of coupon code. I have absolutely no affiliation with either site but if you want to support this site then I'd recommend checking the FAQ and getting to Interview Cake through there.
The only disadvantage is that the site did not have enough mid to senior positions and very little focus on positions for engineering manager and above.