> For the complete documentation index, see [llms.txt](https://yasmeen-rezk.gitbook.io/my-notes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://yasmeen-rezk.gitbook.io/my-notes/bug-bounty-playbook-v2/caching-servers.md).

# Caching Servers

###  How do caching servers work?

Cach servers work by saving a user's request and then serving that saved request to other users when they call the same endpoint.

* The server **only** gets called if the response is not found in the caching server.

**A cache key:** is an index entry that uniquely identifies an object in a cache.

The caching server determines if two requests are identical using the **cache key.**

#### Example

<figure><img src="https://509923538-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FJ2ZeCCTH4XZTY31hlbGx%2Fuploads%2FUmlVFU5heqibTebOaoxP%2Fimage.png?alt=media&amp;token=96c4092a-695a-4b50-a2f1-ea14a63ff197" alt=""><figcaption></figcaption></figure>

* “user 1” requests the “example.com/kop?somthing=ok” -> response not found in the caching server -> forwarded to the web server answering the response.
* users 2 and 3 make the same request -> response found in the caching server -> web server not contacted -> old response shown instead.