Is there overheard to changing a cookie value on each request

Question

Let's say we set a "last request at" timestamp in a cookie on each request. Is there additional overheard to updating this in terms of more data sent over the wire, or do the cookies have to get sent over the wire on each request anyway?

Answer 1

They are only sent from the client on every request, so you will have a small additional overhead from the server.

You're able to test this by watching the headers in the "Network" tab of Chrome, or Firefox with Firebug (or livehttpheaders).

Answer 2

The cookies must be sent anyway.