[Twisted-Python] Proxy server in front of two web sites

[Stefan Arentz]

I'm looking at implementing a solution for the following problem: I
have a setup with two web servers. Each contains the same directory
structure but not the same files. Using a proxy server in front of
these two I would like to merge them into one. So the proxy would
first hit server A and if A returned a 404 then it would hit B.

Is this something that I should implement as a web server or as a
proxy server? Is there actually a difference?

 S.