Navigating to TOP > Service > Applications > Application Instances, the page loads for 5 minutes and eventually shows the error:
Error 503 Sorry, the service is not available Try to reload page later.
There is a vast amount of APS 2.0 application instances (>20000).
The page rendering will get optimized in scope of APS-41694.
Increase Apache timeout to 10 minutes on the Branding node(s) per the instruction from the article: