It wouldn't be that good of a reference. Full disclosure: I led the backend team at Vine a while back.
Vine didn't use a lot of Flask. The main piece that was used was routing (i.e. @app.route). Everything else was custom. Even flask.g was replaced with something that can propagate context properly across greenlets (the method of concurrency we chose), without a lot of overhead. If you're curious, that piece eventually became https://github.com/mikekap/gbatchy though I can't say that's well supported now.
The main takeaway from that codebase is: async needs to be part of the language. Having it be bolted on leads to...unpleasant hacks. I think Python 3.5+ is heading in the right direction there, but Vine was stuck in 2.7-land forevermore (mostly because we wanted to keep pypy compatibility even though pypy was never rolled out; not the best reason).
Vine didn't use a lot of Flask. The main piece that was used was routing (i.e. @app.route). Everything else was custom. Even flask.g was replaced with something that can propagate context properly across greenlets (the method of concurrency we chose), without a lot of overhead. If you're curious, that piece eventually became https://github.com/mikekap/gbatchy though I can't say that's well supported now.
The main takeaway from that codebase is: async needs to be part of the language. Having it be bolted on leads to...unpleasant hacks. I think Python 3.5+ is heading in the right direction there, but Vine was stuck in 2.7-land forevermore (mostly because we wanted to keep pypy compatibility even though pypy was never rolled out; not the best reason).