The website was unavailable for ~15 mins today. I realized it's been a while since run the optimize functions on the database. It seems to have helped... though not by much.

The cache of the shared stories list is a good improvement, however it only saves one relatively expensive query. There is another similar query for the "Recent Stories" that is not cached yet, and I suspect this one also causes a lot of slow down.

I'm going to investigate the design of the database. I've never studied MySQL thoroughly since my main interest in web development is the front end side (Javascript, Css, etc). However I need to catch up on optimization techniques because the stories table is nearly one gigabyte and it keeps growing. Something is not quite right with the way I've designed the table, or the indexes.