Don' forget about IOPS on RDS

A lot of things a slightly different when you run your application on cloud services like AWS. Take database servers: Increased load can always change the performance of DB look-ups and writes. Larger tables can lead to slow queries if the tables are not indexed right, a lot of writes may cause unexpected locking, etc.

However if you use Amazon's AWS there is another important factor you should not loose sight of: IOPS. This measures the number of I/O operations between the database server and its storage, which is attached as network storage.

It's somewhat unclear if/how Amazon throttles the throughput if you don't reserve IOPS. You might be at the mercy of other RDS instances that are running on the machine and probably some kind of rate limit AWS implicitly imposes.

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.