Opportunistic content delivery using delta coding

A client device for receipt of content data over a communication network, the client device comprising:

• a client cache storing cached content chunks comprising a content chunk and other content chunks received from a first intermediate server;
• a user system comprising a client optimizer executed by a hardware processor that:
• receives an identifier that identifies the content chunk of the content data from a second intermediate server different than the first intermediate server,
• determines that the content chuck of the content data and other content chunks of the content data are included in the cached content chunks, and
• generates a response in response to receipt of the identifier that indicates the content chunk and the other content chunks of the content data are included in the cached content chucks stored in the client cache;
• and
• a communications subsystem comprising a client-server communication link of the communication network between the client optimizer and the second intermediate server that sends the response to the second intermediate server and, in response, receives additional content chunks of the content data from the second intermediate server, wherein the additional content chunks do not include the content chunk or the other content chunks.