Auto-Scaling with AWS Spot Instances

While working on inPowered's back-end systems we are using a lot of different AWS services. One of our sub-components recently needed to be able to handle many times the load it had been handling very well for over a year. Since we're using auto-scaling groups (ASGs) for pretty much everything of course the solution was to simply scale up more instances. However we had to go from a few dozen to a few hundred instances almost over night. And even though this ASG was utilizing t1.micros controlling cost became a concern. So we decided to try using spot instances.