The Full HA Cluster starts with a minimum of 3 EC2 instances for the Web Servers. The Database Servers run on Aurora Mysql with 2 RDS instances. The cluster is fully HA and will failover over automatically. The web nodes can be scaled out horizontally as needed. The database nodes can be scaled horizontally with read-only nodes. Staging and admin servers, also VPN, are optional services that can be added on.