> But in retrospect I think Postgres is probably a better fit for what we needed.

Would love to hear more about this.

If after three years you think so only "probably", you probably still aren't confident about your requirements.

You don't say to your girlfriend "We had fun the last three years, but probably I'm better off with my ex" unless you have no clue what you are looking for.

I'm using Postgres for a financial app, and the idea of never updating a value in place sounds very appealing over PostgreSQL's construct of updating in place.

I'd love to hear your thoughts about how using Datomic in this immutable sense plays out in practice, because Rich Hickey's talk in favour of it is compelling. https://www.infoq.com/presentations/Datomic-Database-Value