Does Classic ASP pages called with Querystring parameters are cached by the HTTP-level Kernel cache?

Question

Our company have a website made in Classic ASP, which most of them are static pages. We have enabled Kernal cache for 30 seconds in our web.config file in order to speed-up the displaying of all our webpages :

<caching enabled="true" enableKernelCache="true" maxCacheSize="512" maxResponseSize="524288">
    <profiles>
        <add extension="*" policy="CacheForTimePeriod" kernelCachePolicy="CacheForTimePeriod" varyByQueryString="*" varyByHeaders="accept-encoding, accept-language" location="Server" duration="00:00:30"/>
    </profiles>
</caching>

We have one dynamic page displaying customer information : This page display information based on the Request.Querystring("userId") parameter :

EXAMPLE. https://website.com/user.asp?userId=12345

Our question is the following : Do you confirm me the fact that this dynamic page will never be cached for other users, as it always have a different URL (based on the userId parameter) ?

We need to be sure that userId=12345 will NEVER see cached information for userID=56789, even if they access the "user.asp" page in the same cache timeframe (30 seconds) ?

Thank you very much,

Answer 1

The Kernel Cache in IIS needs several conditions to be met by the requested resource in order to be cached. One of those conditions is that it should not contain any query string. You can check it in Microsoft's Knowledge Base here:

https://support.microsoft.com/en-us/help/817445/instances-in-which-http-sys-does-not-cache-content

if one or more of the following conditions are true, HTTP.sys does not cache the request response:

....

• The request contains a query string.

It makes total sense, and that's exactly the use case that you need.

HTH