I know the authors of this project also read Hacker News, so it probably is better if we wait till them to state their motives. But I suppose I could give a brief first, since most of the confusing comments are due to language barriers(sorry if you don't know enough Chinese, you might not have read enough about this project).

This is actually affiliated to https://github.com/pingcap/tidb, which is another implementation of Google Spanner/F1, similar to CockroachDB. So think TiKV as spanner, and TiDB as F1.

They actually started out using Go. And the reason they are changing to Rust is not trying to be a Rust cool kid, but due to real constraints: Go's GC introduces too much of latency time (and no, Go 1.6 is not enough despite being better), they are also not satisfied with cgo's costs. That's why they are changing to Rust. Note that according to their words, they still love Go better, and TiDB is also happily using Go. But for TiKV's case, Rust is perfect.

Disclaimer: I'm not working on TiKV or TiDB, I'm just a fan of their work(they are also the founders behind Codis: https://github.com/CodisLabs/codis, tho not working on that anymore). I'm happy to list references on where I got all the information in case anyone are interested but they are all in Chinese, which I think might not be that polite since not everyone here reads Chinese.