Has anyone ever decided to create their own database or k/v store

So I've been in a job search for about 2 weeks. And it's going...

With that said I have been unemployed for longer than a week in 6 years, and prior to that I was employed nonstop for 6 years before that. So I haven't been unemployed in any meaningful was for basically 12 years. But I see developers WAY smarter than me still struggling to find work, so what hope do I have

I didn't want to talk about that. I just wanted to say that I have time on my hand. And I figured I would like to build my own key/value store. I know it's not practice as there are a crap ton in the market right now. But I am just interesting in building on. And I think it's a form of upskilling. I mean backend engineering with Kafka, databases, cloud, load balancer is as comfortable for me as drinking water at this point. Sure it can be challenging, but not a challenge I don't think I can't overcome (from a technical perspective). Most challenges in backend engineering just come down to management, tech debt, and company constraints. But those are process challenges not technical challenges (still important though).

Anyway has anyone had experience building a key/value store? I'm a Go developer and have been wanting to cut my teeth on some low level programming for awhile. I could build it in Go, but I want to use a non-GC'ed language. I'm loving Zig right now. Anyway I do know that most k/v stores are LSM trees and they often have Memtables based on Red-Black trees. I have looked the the source code for a few key value stores. So I kind of sorta know what they're doing under the hood.

Anyway would love to know your experiences. Challenges? Did you feel it was a waste of time?