in reply to Re: Store results by search term, not session ID
in thread Database searches with persistent results via CGI
I think the problem in their case came from how much the Java servlet session interface looks like a cache. It's very tempting to just cache things in it rather than build your own proper cache. This is something to be wary of with Apache::Session too.
(Incidentally, some of the other posters did mention the idea of using the search terms instead of the session. They just weren't as clear about why.)