is there an implementation of B+ trees that fluidly pulls from disk vs RAM? e.g., two B+ trees, one in RAM and one on disk, with the RAM one evicted with sieve caching? possibly a very lite WAL? something that lets you use a B+ tree bigger than RAM, and persist to disk
Pretty much every OLTP database contains an implementation of that.
https://www.youtube.com/playlist?list=PLSE8ODhjZXjYMAgsGH-Gt...