For what it's worth, SQLite works just fine for some blockchains without Rust extensions, e.g. nimbus-eth2[+] uses SQLite with `journal_mode = WAL` to locally persist Beacon Chain data.
Other Beacon Chain client implementations (there are several in wide use) may use SQLite, or something else, I'm not sure at the moment.
https://news.ycombinator.com/item?id=32725455