I recently started using a free postgresql database service provider and within a few months they folded and got acquired/hired by some bigger company and sunset the entire product with a short notice (it was on the front page of HN). Meanwhile, elephantsql continues to serve me, even though the free tier only allows tiny 20MB databases so I can play with postgresql easily. Not that I do it everyday or even every week but it is there when I need it.

I mean you should limit the free users to a point where you aren’t worried about the whole thing collapsing under the weight of free users.