I am running an Elastic Load Balancer backup by 2 instances in different Availability Zones in US East. I am using Multi-AZ RDS as well. Ideally this should ensure that if one AZ goes down, it should not effect the app because everything is spread across multiple AZs.
But the recent AWS outage took the app down for a long time. I am not sure how this can happen. It would be great if someone can point out what went wrong.
Major question here I have is how can I avoid this in future? I can setup app servers across different regions or even providers and use DNS for load balancing but what do I do with MySQL? Read Replicas will introduce some lag which I would want to avoid.