It's because Datomic doesn't have the object/relational impedance mismatch. Because immutbility yields idealized caching so a lot of hard performance problems inherent to RDBMS go away. It's like moving from CVS to Git.

Fuck it, hyperfiddle isn't launched but lets just post it here. Hyperfiddle is JSFiddle + Datomic. http://hyperfiddle.net/ If you care about this, you should reach out, please email me!