I don't care so much about optimized tight loops written in assembly, rather about the ability to scale nowadays. Datomic uses databases like you describe e.g. Postgres as its storage. So it would be foolish to say that it beats their performance on a bare bones level. Instead, Datomics architecture and information model make it much easier and significantly reduce the overhead to design and implement applications that provide insane performance. I won't argue that you can hand rewrite every Datomic application in its underlying storage database and get more performance out of it if you do your caching and coordination right. It will take you much longer though (I'd guess a tenfold at least), likely have some very difficult to find bugs, and the result won't be as easy to extend. With Datomic, I get memory speed performance out of the box for the heavy hitters and so much more that it take would take some very uncommon requirements for me to choose something else nowadays.