Caching vs CDN

Cache(ElastiCache)

Again caching is storing data that are frequently accessed into RAM so that they can be retrieved more quickly than going through a disk / a database query which takes significantly more time on CPU scale.

CDN

Content delivery network is a network of proxy servers that are placed in different geographical locations all around the world. The goal is that rather than having the user say in California make a request to a server that is in New York to request content, you place those website contents in CDN so that they can be retrieved quicker by making a request to the CDN server closer to the user.

Cache and CDN

They both share the purpose of retrieving content quicker for the user.