Too Long; Didn't Read
In order to build <strong>HA</strong> & <strong>Resilient</strong> applications in <strong>AWS</strong>, you need to assume that everything will fail. Therefore, you always design and deploy your application in multiple <strong>AZ</strong> & <strong>regions</strong>. So you end up with many unused AWS resources (Snapshots, ELB, EC2, Elastic IP, etc) that could cost you a fortune.