I have set up an EKS cluster and I am trying to connect application pod to ElastiCache endpoint. I put both in same VPC and configured in/out security groups for them. Unfortunately while trying to telnet from pod to cache endpoint, it says "xxx.yyy.zzz.amazonaws.com: Unknown host". Is it even possible to make such a connection?
Yes, if the security groups allow connectivity then you can connect from EKS pods to Elasticache. However, be aware that the DNS name may not resolve for some time (up to around 15 minutes) after you launch the Elasticache instance/cluster.