Migration from Postgres to Datomic
This comes up every time Datomic is mentioned, but it's tremendously sad to see such a revolutionary technology lack any sizable adoption because of its licensing model.Datomic packages up a CQRS + event-sourced architecture in a really nice way.  You can stash graph/tree/relational/tabular/(insert shape here) data and query it out with the powerful Datalog language.  You get time travel (versioning) for free.  Etc, etc.It's a crime that this hasn't taken off as one of the leading data stores; hopefully Cognitec has some sort of roadmap to an open source release.