At approximately 5:10 AM ET, one of our load balanced web servers in one of our data centers began throwing 500's on certain requests. Our load balancer did not catch this in time to remove the failing server from the pool, but our monitoring systems did. This means that a small portion of On Demand customers that were active at this time were seeing these errors.
Service was restored by 5:16 AM ET. I will examine the symptoms of this outage and find a way for our load balancer to detect this.