The AWS East Region outage showed all of us the importance of running our apps and databases across multiple Amazon regions (or multiple cloud providers). In this post, I’ll try to explain how to build a MySQL (or Amazon RDS) redundant site. For simplicity, we create a passive redundant site. This means that the site is not used during normal operation and only comes into action when the primary site crashes. There are many reasons for choosing such an architecture – it’s easy to configure, simple to understand, and minimizes the risk of data collision. The downside is that you have hardware just sitting around doing nothing. Still, it’s a common enough scenario. So what do we need to do to make it work?