I think it's a proxy between your software and SQLite with a new database API. I guess "multiplexing" is a big word for saying you can someday swap SQLite for something else.

The CLI shows key-value store features.

I don't know if this software has real world savings in performance. I don't think I would ever use this software.

Like if you want your frontend to write to both Sqlite and RocksDB?

I guess they mean number of frontends times number of backends? https://github.com/buffdb/buffdb/issues/19