Salesforce runs Salesforce on postgres with LSM:
replyhttps://vldb.org/cidrdb/2026/a-multi-tenant-relational-oltp-...
Likely their own fork, not plain PG.
replyOrioleDB seems interesting, not sure it's what you're after but worth a look.
replyIt is, but it's not usable right now without some patches to postgres. At least that was the case as of PG17, and very likely 18 too.
replyContext: https://www.orioledb.com/docs#:~:text=OrioleDB%20currently%2...