Ok. In short what happened:
1. YL showed Garvin the new backend. He liked it -> we will proceed.YL got much needed input about detail questions.
2. The next step will be to make some tests with users.
3. We realized that there is a conflict between our two aims to 1. relase the new backend as fast as possible and 2. to implement new featues like a db-layer. Kind of an answer was to try to do 1 regardless of the new features, while developing them in feature-branches and merging when possible without real breakage, which I think should be possible.
4. Mattsches suggested that Unit-Tests could help with that (I agree)
5. In the end, we had a short talk how to notify YL or me about bugs and where our TODO-list is (on paper so far in my case), so we spontaneously decided to use githubs issue tracker
with labels for that. See http://board.s9y.org/viewtopic.php?f=11&t=19451
Please add if I forgot something.