This is one of the deepest deep tech startups I've seen in a long time.
I had the pleasure to meet some of the folks at RustConf in Portland.
Readyset is basically reimplementing a full database, at the absolute bleeding edge of db research, enabling global partial replication of any kind of data.
A solution desperately needed, as databases grow.
You can think of it as an intelligent LRU cache in front of your database. An important step towards fast globally distributed applications.
I hope this project will get more publicity and adoption - it's very well deserved.