AWS Elasticache Memcached support allows auto-discovery to dynamically manage memcached nodes in the cluster. Amazon ElastiCache Cluster Client is an enhanced PHP library to connect to ElastiCache clusters. This client library has been built upon libmemcached and is released under the Apache License. https://github.com/awslabs/aws-elasticache-cluster-client-memcached-for-php/releases

Current Joomla release as of today (3.6.5) does not support AWS's autodiscovery of nodes and design is based on configuring static nodes in a multi memcached cluster. As of today, the static feature is not fully implemented and will require you to update your configuration if new nodes or failures occur in your cluster. This is a new feature request to support the PHP autodiscovery fork.