I don't think Datomic takes that long to wrap your head around, but it does take a long time to actually use. There's no inherent equivalent of Model.all or Model.where(x = y), so chances are that you'll have to write your own DSL for mapping domain objects to datomic queries which is a time consuming non value-adding activity. You'll also likely want to transact through some DSL so that you can do validations, and post-creation lifecycle hooks, where in Rails or something you'd just get that for free. The Devops is pretty frustrating imo, there's no equivalent of the Heroku Postgres or AWS RDBMS one-click deploy for Datomic, so you'll need to set it up and monitor it yourself, which can get tricky when doing things like REPLing into the db from your local Emacs shell can crash a process downstream somewhere because you went over your remote peer limit without realizing it. And there's no view that shows you the IP address of every connected peer, so it's kind of hard to debug what exactly is going on sometimes. I think the query engine is really cool, I just feel like I waste a lot of time using Datomic that I don't with other databases.
