I'm definitely not a DB guy, but Datomic was the first thing that came to mind. You could also include databases that require linear consistency like etcd if yo

I'm definitely not a DB guy, but Datomic was the first thing that came to mind. You could also include databases that require linear consistency like etcd if you consider "functional databases" to be any database that represents state as a function of time. There was an early slide that explicitly said FRP and functional databases were inspiration for the compiler design, but I do agree that the title should have reflected that fact.