Dave said "this preceded NoSQL I imagine", and he was referring to key/value stores in general I believe, which are indeed older than relational databases and are a layer on top of which relational databases are built.

When I initially heard it, I thought it referred to Redis specifically, and I thought "no way, Redis came out in the middle of the NoSQL boom".

I was wrong, by two days. :-D

Redis came out on 2009-05-10 and the term NoSQL in the current sense was coined on 2009-05-12.

https://en.wikipedia.org/wiki/Redis

https://en.wikipedia.org/wiki/NoSQL#cite_note-20