I can pretty consistently get app_server's memory usage to jump into the hundreds of MB and stay there even after closing WebPositive by browsing various pages on vimeo.com's blog. (I discovered this inadvertently while trying to reproduce a totally unrelated bug; I wanted to find some videos to browse on Web+, but it seems all video, not just YT, isn’t working at the moment.)
I checked listarea, all the memory seems to just be in the heap.