If RDS or other “hard to replicate very quickly during disaster” infra is being run I personally would still have cross A-Z replication at minimum, to reduce network costs I would configure the “other zone” as a backup replica only and not for performance clustering.
With automation we can spin up full new compute stacks, including load balancers and DNS in about 5-10 minutes per “unique” environment configuration.
While it guarantees we could never have a no downtime failover, we’re okay with it and have more than halved our network costs (which admittedly were about number 8 on our AWS bill by cost).
If AWS has a regional outage this service is so far down the list of services to recover/restore that it probably will be overlooked. Accept the increased risk for the cost savings since it meets the reliability requirements of the service.
With automation we can spin up full new compute stacks, including load balancers and DNS in about 5-10 minutes per “unique” environment configuration.
While it guarantees we could never have a no downtime failover, we’re okay with it and have more than halved our network costs (which admittedly were about number 8 on our AWS bill by cost).