[einhverfr]

It's not about the size of the database or deployment. It's about the number of applications interacting across the same relational interface. The fact that applications can turn off strict mode is a big blow in this area. You can't be sure your data is "obviously correct" to paraphrase a different HN post.

One of my customers logs certain web data into a MySQL database and loads/processes it in a PostgreSQL database every day. The data is then accessed in Pg by at least three different applications.

That's reasonable, btw.