When I see products like this, my first question is: could you write an free, open-source app with this without having to shell out your personal money to make

When I see products like this, my first question is: could you write an free, open-source app with this without having to shell out your personal money to make it happen? For Amazon Cognito, the answer appears to be "yes, until all of your users together store more than 10GB". ie. until your app gets popular. So for free open-source apps, I think I'd prefer to stick with Dropbox or Google Drive, where the billing is associated with an account the user already has (which most users can operate entirely within the free tier). That way you don't run into a situation where you are a victim of your own success, by exceeding a free tier that applies to the sum of all user data in your app.