Could you explain a bit about your decision to use Flask + extensions rather than just Django? It seems like you started with Flask and added a bunch of extensions to provide most of the things that Django provides out of the box...
I'm not the author, but I just picked a Flask / Backbone stack over Django (after initially starting with Django) because so much of Django didn't seem to fit. Django wanted me to make a server side template based CMS. All I wanted was something where I could make a server that talked mostly JSON to clients. (My web application controls and displays results from using some custom hardware and will serve at most tens of users.)
Also, because I don't need teh web scalez, I'm using Postgres. For fear of making things completely undevelopable for hires outside Silicon Valley and NYC, I passed on stuff like Coffeescript and SASS.
Are you implying that you can't use Postgres for web-scale services?
I think the implication is that he/she doesn't need some exotic combination of SQL and NoSQL databases in some complicated stack for scaling.
No, I'm just picking on the HN groupthink.
While I can't speak for the authors, I personally have been building out some sample apps with Tornado + Backbone. Since as it's working out Tornado provides a very scalable data layer with a minimum of fuss.
As someone who literally started using tornado a few days back, I can completely agree about the minimum fuss part. Though documentation is a little sparse atm, it has a fairly small code base. I was a little surprised it didn't come with a sessions module.
IMHO - Sessions don't make sense at scale. When you have sessions you usually cache objects in sessions, which means you need complicated update mechanisms. Better to store the objects in Redis and just have a single update...
What is good in Django is mainly it's ORM, which we don't need. Its templating system sucks, and also its memory usage and performance otherwise.
Did you consider Pyramid? It's insanely flexible, has amazing documentation, doesn't make any assumptions about the kind of applications you want to build with it and has a "pay only for what you need" philosophy. I'm currently using Django for my projects because it's a good fit for them (CRUD apps that generate static pages; zero frontend wizardry), but if I were to write a frontend-heavy webapp that talked to a server using a JSON API, Pyramid would be my first choice.
And if you really need a good ORM at some point, you can just us SQLAlchemy which is a lot nicer anyway.