Last I checked it is still possible to send an email from inside a Rails controller, or to update a bunch of database records in a tight loop. You can't do thes

Last I checked it is still possible to send an email from inside a Rails controller, or to update a bunch of database records in a tight loop. You can't do these sorts of things at scale, which a lot of people are still learning the hard way. Part of an app server like Django et al being flexible is giving you the ability to shoot yourself in the foot. It is much harder to screw something up royally when you are working within the CouchApp constraints. That's what I meant by fragile. Google App Engine gets this mostly right by enforcing draconian timeout limits and other constraints, so it is much harder to write an app that is gonna fall over under a big wave of traffic, as the sandbox will complain right away. CouchApp is even more picky. The programming model doesn't have operations that could block on remote IO, so you can't even go down the bad path. Of course, when you do need to send an email, you've got to rethink how to do it. (Actually in a real app you'd do email from an asynchronous task as well.)