The bigger problem with Tornado is that its async paradigm infiltrates every single layer of your business logic, and there's no good way to abstract away from that. Every single function signature and invocation style becomes affected by that, which is naughty.

At the end of the day, Python both as a language and as a technology just wasn't built with these things in mind, and that's why it constantly feels like you're doing something wrong when dealing with async and event-driven programming.

Bottomline is, as amazing as Python is, if you find yourself building an event-driven asynchronous system in it, perhaps you should consider an alternative stack.