I have only single worker node running in EKS Cluster. Due to cost issues, I am looking to scale it down to 0 in off hours as this is dev cluster.
I have all the application pods, ALB Ingress, Load Balancer controller and cluster autoscalar running.
What will happen if I scale my worker nodes to zero?
What will be the impact of this, will the ALB gets deleted?
All your workloads will be shut down. Essentially, your cluster will not be operational (which is obvious).
The ALB will not be deleted since its managed by the ALB ingress controller that keeps it the state in etcd (managed by AWS EKS). So as long as your cluster is not deleted, the ALB shouldn't be deleted.
Keep in mind that if you delete your cluster before deleting your ingress service (without your ALB ingress controller starting up again) your ALB will be left dangling since there won't be a controller to reconcile and remove the the ALB.