There have been some outages during peak-times over the last several days (coincidentally since I upgraded the servers… all I did was beef up the ram and give some of that to memcached though, so I’m thinking it’s just coincidence).
I think a large part of the cause is that we have a bunch of new users of the API which is rather database and server intensive (since the title-matching is fuzzy).
Just last week we added CantoPod to our list of users, now we have the even more popular GimmeSomeTune iTunes plugin. Each popular plugin generally means tens of thousands of extra requests for lyrics per day.
As soon as I can figure out how to configure APC (op-code caching for PHP) and then Squid, services should be back up to speed.