In the past each “9” on your availability cost about 10x more. So for example, 99.99% availability cost 10x more than 99.9% availability. Amazon is making inroads into these costs.
Amazon Elastic Beanstalk already offers inexpensive load balancing that will direct users to working nodes and even start additional nodes when demand increases. That’s great but how can you ensure availability if the load balancer goes down due to fire, flood or software error?
From today you can use Amazon Route 53 DNS Failover. You can now have a hot backup of your primary system in a different availability zone (or continent) and if your primary goes down Route 53 DNS will route your users to the backup node.
A nice touch is that rather than have a hot backup you can have an Amazon S3 website that says “Normal Service Will Be Resumed Shortly”. This is a very high value, low-cost feature.