We recently mentioned over 100 presentations from Portland’s OSCon made it to the web. Included was a surprisingly open presentation on Facebook’s backend.

There was a timely discussion on the subject over at Metafilter. The question posed was “How does Facebook handle or simplify the presumably complicated database queries involved so that me loading my page doesn’t bring it to its knees?”

The answer, according to the presentation by Facebook’s Lucas Nealan? Memcached. In fact, a staggering 400 plus memcached hosts with over 5 terabytes of memory. That’s more than your typical network solution. Memcached is a way to cache frequently used database queries in memory for easy serving.

It’s not just Facebook’s secret. I recently had the opportunity to speak with Garrett Camp, founder of StumbleUpon who praised Memcached ability to dramatically reduce their load.

“Memcached has helped a lot. We added memcached to a lot of our most common queries and load has dropped off to about a third,” Camp admitted. “Between basic partitioning, a lot more RAM, database boxes and memcached, a lot of our most urgent pain points in the past six months have kinda disappeared.”

Below is Facebook’s presentation: