Except running memcached on an EC2 instance is not equivalent to the ElastiCache offering. With ElastiCache you are paying for a redundant, managed service that can be scaled and monitored through a few clicks of a webpage or API.

Outsourcing these type of things is potentially justifiable to a developer whose wallet is full and many hats touch the ceiling.

In what way is ElastiCache redundant?

> In addition, Amazon ElastiCache automatically detects and replaces failed Cache Nodes, providing a resilient system that mitigates the risk of overloaded databases, which slow website and application load times.

Or membase, which gives you storage-backing and TAP protocol to do things like fetching all keys.