You reckon? I would have thought Wikipedia a textbook case for a great big cache. I would have guessed that the great majority of their views were read-only by unregistered users, with the pages in question following a power law distribution. Hm, would be interested to find out more about that.<p>update: I went and looked it up. They do indeed have a great big cache, many of them in fact. In fact their Amsterdam presence runs <i>only</i> cache! From what I can tell, it seems their bottleneck is actually Apache, and presumably a lot of that is PHP.<p>Interesting presentation here: <a href="http://wikimania2009.wikimedia.org/w/index.php?title=Media:Rob_Halsell_-_Wikimania_2009_-_Wikimedia_Operations_%26_Technical_Overview.pdf" rel="nofollow">http://wikimania2009.wikimedia.org/w/index.php?title=Media:R...</a><p>Also check this out: <a href="http://ganglia.wikimedia.org/pmtpa/?gw=fwd&#38;gs=Wikimedia%40http%3A%2F%2Fganglia.wikimedia.org%2F" rel="nofollow">http://ganglia.wikimedia.org/pmtpa/?gw=fwd&#38;gs=Wikimedia%...</a><p>Go down to the MySQL section. Plenty of headroom, but the Apaches are working hard.