MySQL connection on Amazon RDS t2.small performing very slow

One of the things that we ran into with a small RDS instance was the # of connections setting. It's a formula based on RAM - and it only allows ~ 150 connections on a small DB. That's the first thing that I would look at.

SHOW PROCESSLIST;

would be the command. If you are not using some sort of connection pooling in your app, I could see hitting that limit fairly quickly.

Just a shot in the dark, but good luck anyways!

http://www.mysqlperformanceblog.com/2010/09/10/cache-miss-storm/

As it turns out, our issue was a cache storm miss, AKA miss stampede.

We've solved it by implementing a 50% cache expiry. Basically for every item in memcache we create a second cache item with a similar key plus the appended 'regenerate' string. This item expires at exactly 50% of the typical cache expiry time, indicating to the next request that we're getting closer to expiring cache and the next request will need to try and regenerate cache.

This prevents the storm of users trying to regenerate cache at the same time and ensures our cache has the best chance of always staying fresh!

A Tricky one to track down!