Varnish web cache does this by default - it is called requests coalescing or collapsing. To find more about it check this - https://info.varnish-software.com/blog/request-coalescing-and-other-reasons-to-use-varnish-as-an-origin-shield
We collapse requests so your setup doesn't
The big bad wolf of content distribution is something called the "thundering ...
The best way I found so far to diagnose ssl session resumption is to look at the sent byte count
First, enable mod_status and set ExtendedStatus to On. Make sure this status page is non-public accessible, probably with ACL or basic authentication with strong password.
You should be able to see session cache usage from your httpd status page, something like
As indicated in the comments by Gerard H. Pille, the operating system's page cache will make sure the hot data is stored in memory.
In terms of Varnish this means you can use the file stevedore to store the objects.
Here how you would configure this:
varnishd -s file,/var/lib/varnish/storage,250G
I only focused on the -s parameter in the ...