I'm using Tornado instead of Flask. When I was evaluating Flask vs. Tornado, I found Tornado to be much faster than Flask. More importantly, Tornado is much more straightforward. I actually prefer putting all URL in one place (tornado) instead of using those @route decorators(flask,bottle). On Flask, if you want to write anything more complex than HelloWorld or ToDo, you use something called blueprint, which is not easy (at least for me) to understand.