We would like to use AWS ElastiCache for our application, and we have a strict requirement that all data should be encrypted in transit.
I was trying to find out whether ElastiCache access is done using SSL but cannot get a definitive answer from Amazon documentation. It is possible to set a policy option aws:SecureTransport to True when setting security for ElasticCache cluster, but I am not sure if it is supported for ElastiCache. AWS documentation says that this option is ignored e.g. for S3 as S3 always uses SSL.
ElastiCache now supports TLS encryption in transit.
https://docs.aws.amazon.com/AmazonElastiCache/latest/red-ug/in-transit-encryption.html