[funcDropShadow]

Admittedly, my experience with MongoDB and Cassandra has gained some rust over the last decade, but what makes you say such nosql databases have expressive APIs? Compared to PostgreSQL they have miniscule query languages and it is very hard, if at all possible, to express constraints. And constraints, sometimes self-imposed sometimes not, are what makes projects successful, even startups. Many startups try to find this one little niche they can dominate. That is a self-imposed constraint. People tend to think freedom makes them creative, productive, and inventive, while in fact the opposite is the truth. With opposite of freedom I mean carefully selected constraints not oppression.