Created a freshly built 7.900 server platform
Bare bones configs: web browsing and WebAdmin responding "normally".
I took my old 7.504 config and uploaded (Astaro configured to manage web browsing using transparent proxy)
WebAdmin took excessive time to load from login - circa 10 minutes
Web browsing very, very slow responses.
Disabled web proxy - WebAdmin and web browsing returned to near normal.
Not tried playing with Web proxy config yet - are there any known incompatibilities between the 7.504 config and 7.900?