Java API folder.getChildren() is taking time

Hi,

I am fetching a folder tree with java API and i am facing that the call folder.getChildren(["some","fieldnames"]) is taking some time. In one case it takes 20 Seconds before the iteration over the 140 files that a folder is containing starts. Is there any way to speed that up? Or Is there a rate limit by Plan or so? or do you have some ideas for improving?

Regards
Horst