If simplicity and lack of migrations is the only advantage of MongoDB then there is no reason to use it in place of Postgres, since you can just use JSONB instead and not worry about any of those.
Re:Ask HN: Go-to web stack today?
by jacques_chester on Saturday January 05, 2019 @10:54AM
(#18832214)
> with Postgres we also had to deal with schemas and migrations.
Schemata are good things. Migrations are the database insisting on tedious bureaucratic nonsense like "don't blow your foot off" and "don't regret this later".
> Technically you could also use JDBC in a reactive manner, but it looks unlikely to work with the frameworks we use with Postgres.
The Spring team are pretty keen on removing that gap: http://r2dbc.io/
> with Postgres we also had to deal with schemas and migrations.
JIC, this is exactly what I meant with "paying that debt upfront". If your model does turn out to be relational and you don't have this, you are going to get burnt, badly.
We can also easily leverage reactive streams with reactive Spring Data. Technically you could also use JDBC in a reactive manner, but it looks unlikely to work with the frameworks we use with Postgres.