You really have senior people? Isn't interview practice something that's mainly interesting to junior candidates?
Technical interviewing is scary and hard for everyone. We get a lot of senior engineers signing up in large part because they're senior. Imagine you've been at Google or Facebook for a number of years and are starting to think about your next job. You've been on the interviewer side of technical interviews a lot, but it's been a while since you've been an interviewee, and all that nice algorithmic stuff you were so good at in college just isn't top of mind anymore. And you're freaked out a bit because there's so much sparkle around your employer's brand that it's going to be embarrassing to bomb the first few warm-up interviews you'll inevitably do.
Before interviewing.io, you'd probably schedule some throwaway interview with companies you didn't care about and hope for the best. With interviewing.io, you can schedule a bunch of anonymous practice without anyone judging you while you warm up.
As one of our very senior users put it recently,
I think your product is fantastic. It's been ~7 years since I was last on this side of the interviewing table, so this is a very nice way to test the waters a bit as I decide on the next steps for my career. I highly value the anonymity.
The other reason senior candidates like us is that we make it so much easier for them to line up interviews once they're warmed up. Instead of applying online, digging up old recruiter emails, or haranguing their friends for referrals, they can quickly and easily skip to the technical phone screen, saving them weeks of time.