Original objects are never modified, but transparently wrapped by observable proxies.

Proxy = observable(object) Creates and returns a proxied observable object, which behaves just like the originally passed object. The original object is not modified.

use an intercepting proxy server with a built-in cache

Also known as an intercepting proxy, inline proxy, or forced proxy, a transparent proxy intercepts normal application layer communication without requiring any special client configuration. Clients need not be aware of the existence of the proxy.

Intercepting proxies are commonly used in businesses to enforce acceptable use policy, and to ease administrative overheads since no client browser configuration is required.