i didn't mean in general, i meant in this forum application that would do MANY recursive queries and updates to the same table on the same page.
lets say you get 5,000,000 page views a day to the forum: you probably have to get everying done in under 2 seconds to keep the server alive. with recursive queries to a table that is actively getting updated, and current data is crucial, then it would probably start zonking out earlier than 500,000 records.
i have a small mysql table with something like 10 million records and everything still works fine... it is almost solely selected from though, and everything is very well indexed