This made me curious - are there any SQL databases being actively developed in Rust? I found one on GitHub (LlamaDB) that does not appear to be maintained.

TiKV (https://github.com/tikv/tikv) is a database (KV-store to be precise) written in Rust and speaks MySQL protocol.

Toshi (https://github.com/toshi-search/Toshi) is Elasticsearch-like engine that uses tantivy (Lucene-like), both also written in Rust.

Same with https://github.com/mozilla/mentat/

https://github.com/indradb/indradb is a newer db in alpha.

https://github.com/spacejam/sled is also in alpha but is being actively developed.