[timewarrior]

Thanks for raising this good point. I didn't get a chance to elaborate on this in my original post because it was getting too long and it was end of a long day.

The cost of adding a column is zero, in terms of schema migration. So that helps with developer velocity. We used an ORM (mongoose), so that we can have added constraints including default values. But Mongo did help us avoid the friction of adding columns.

[Jean-Philipe]

We also used mongoose, which is awesome. In retrospect, I actually wish we had kept mongodb as a read-only database and used postgres as the source of truth. Our data was mostly read-only, with some rather complex relations behind the scenes.

For quick prototypes, I still prefer mongodb.