Explore the use and configuration of HTTP/2
HTTP/2 should allow for more simultaneous and reused connections to the server. As far as I know I just need to compile apache with it and enable it and it should "just work". Combined with OpenLayers being told to make more tile requests at a time this may be faster for loading tiles.
We may hit limitations with how we do proxy'ing since some/most browsers only support HTTP/2 for HTTPS connections and with HAProxy for gamma handling the TLS connections it may not be able to do the HTTP/2 connection all the way to MapCache