Agree, and the "Mongo and Jepsen" page isn't targeting distributed systems experts, most of them know to stay away, because even if there are things that mongo does right, other systems do it better.

What other systems would you recommend?

I don't consider myself an expert in that area. Just someone who learned a lot from Kyle's articles.

Based on this, my understanding is: most of the time you want a relational database. If a relational database becomes a bottleneck for certain data, and you don't want to do typical scaling solutions for relational data, then you need to know what you'll trade for the higher performance. Based on what you trade, you then decide what kind of data store you will use.

What do you want to do?

FoundationDB

Isn't that too low-level?