[inetknght]

I am struggling to understand how it is bogging down requests with data that are "unrelated" to the session.

Cookies are delivered with the request. If it has feature selections, great, no more work necessary on your part.

If the feature selection is hidden behind a user ID, then you need to look up the user ID in a database and then request the user's features.

Indeed, it seems to me that requiring a login in order to customize the viewing experience is what bogs down requests.