It's definitely a very slow database. You have to be extremely fortunate to have a problem that fits into its niche neatly. I'd sooner figure out a historical insert-only schema for PostgreSQL in future. They're not great about fixing problems with Datomic either, it feels like an afterthought. Means of overflowing labor not currently allocated to a Cognitect contract gig, not a priority in its own right.
I think they've improved a lot WRT fixing problems--we had a chat with them after some issues with Datomic in production, and since then (6 months ago) we've had every problem we've discovered get fixed very promptly, and Datomic's continued to scale for us.
coolsunglasses - Why did Datomic seem slow to you? Can you describe the problems you had in detail? I'm not from Cognitect, just someone who is developing some prouducts that currently use Datomic among a few other databases.
Would love to hear some honest feedback. Maybe your struggles were because of the tech, earlier versions, bad hardware config, or mis-applied use case?