Which solution would achieve the requirements with MINIMAL cost?
Use AWS Lambda to create daily EBS and RDS snapshots, and copy them to the disaster recovery region. Use Amazon Route 53 with active-passive failover configuration. Use Amazon EC2 in an Auto Scaling group with the capacity set to 0 in the disaster recovery region.
Use AWS Lambda to create daily EBS and RDS snapshots, and copy them to the disaster recovery region. Use Amazon Route 53 with active-active failover configuration. Use Amazon EC2 in an Auto Scaling group configured in the same way as in the primary region.
Use Amazon ECS to handle long-running tasks to create daily EBS and RDS snapshots, and copy to the disaster recovery region. Use Amazon Route 53 with active-passive failover configuration. Use Amazon EC2 in an Auto Scaling group with the capacity set to 0 in the disaster recovery region.
Use EBS and RDS cross-region snapshot copy capability to create snapshots in the disaster recovery region. Use Amazon Route 53 with active-active failover configuration. Use Amazon EC2 in an Auto Scaling group with the capacity set to 0 in the disaster recovery region.
Explanations:
This option leverages daily EBS and RDS snapshots, which meets the 24-hour RPO. The Route 53 active-passive failover configuration ensures that traffic is routed to the disaster recovery region in the event of a failure. The EC2 Auto Scaling group with capacity set to 0 ensures minimal cost in the DR region.
Using an active-active failover configuration would incur additional costs for always running instances in the disaster recovery region, which is not necessary for a pilot light approach. This does not align with the goal of minimizing cost.
While this option uses ECS to manage tasks, ECS is over-engineered for this use case compared to using Lambda. Additionally, using ECS and Route 53 with active-passive failover would increase complexity and cost without providing additional benefits.
Although EBS and RDS cross-region snapshot copies are a valid solution, using an active-active failover configuration would lead to unnecessary cost for always-running resources in the disaster recovery region. The cost can be minimized with active-passive failover instead.