[Twisted-Python] What is blocking code?

[stephan]

When I started coding I though I will just add the deferred calls where
necessary later. Now it seems to me like I have to change the whole
architecture of my app. 

I am running twisted as a Web-server to serve .rpy files. In these files
I create quite complex html pages. In that process I also access a
database. So when I tried to adapt to the adbapi I encountered proplems
because:
     Starting from the .rpy file I call a method, which calls a method,
     ..., which calls a method, which eventually calls a method that
     queries the database. 

->So where does my blocking code start? Is it just the last method that
  queries the db or is it the first one of the chain?

->Is there a way to make my db call deferred without reversing the whole
  method chain?

->Why don't I just make all the code in the .rpy deferred?


Help very much appreciated.

_stephan