The author does mention Datomic at the bottom of the post, along with CQRS (by which he most likely means storing events) as other options. HE then mentions that he's stuck using an RDBMS so Datomic is not an option.
The one thing I would add is that using an RDBMS does not preclude you from storing events along with your relational data. So you have a representation of current state, but also all of the events that took place to get you to that stage. And that will give you the same type of history.
It's a very cool feature of Datomic that the storage engine is pluggable, and easily changed depending on the characteristics of your data. Using Postgres is trivial:
lifexkills|10 years ago
The one thing I would add is that using an RDBMS does not preclude you from storing events along with your relational data. So you have a representation of current state, but also all of the events that took place to get you to that stage. And that will give you the same type of history.
straws|10 years ago
http://docs.datomic.com/storage.html#sql-database