I would just like to point out that Hasura is a PaaS. More like heroku, but with some ready to use microservices to get started quickly. So with hasura-db (which is a wrapper over Postgres) you get a BaaS like thing that helps you prototype and use quickly for permission safe REST + document operations, but always let you switch to custom code-driven-database operations that we usally write for applications.

And what would be that lesson?

That it's a huge mistake to use a BaaS for anything but a demo. I think it's good to abstract out certain details that don't pertain to your application logic, and that's precisely what something like Heroku does. In my experience, a BaaS adds barely anything to that, and subtracts way more in terms of flexibility and lock-in.

The amount of administration that using a BaaS saves (as opposed to something like Heroku) is minimal; the time that you'd spend doing straightforward admin stuff is just moved over to working around limitations of the BaaS, and is often multiplied in the process. The amount of actual code that using a BaaS saves is between 100-400 lines for a web application. Awful deal.