I'm in a pickle. I had thought my server was in Canada, but turns out it is in France. I don't have the time for a server migration right now (it's the end goal as 75% if the visitors are USA).
Using the website speed test on pingdom, the first byte wait is around 140ms when I test it from Sweden. When I test from California it's around 680ms. I need to try and reduce this as Google say it is slow to crawl the site and overall most visitors are from the US so I need to improve their experience.
Cloudflare is caching static assets so while the latency is also in the 600+ region for css, js and images, they fall right down once Cloudflare picks the files up. My focus is now in php files.
I am unable to use nginx as I cannot do a 100% html cache via a proxy. I can however use redis to cache 99% of the HTML. I have upgraded to php7 and Apache now works with it via fast CGI. I have made the site as quick as I possibly can with heavy memory caching and getting rid of all unused modules etc. This site is quite quick with tests from pingdom in California taking 2-3 seconds to fully render a page that does not hit the HTML cache. However if I can get rid of some of that 600ms delay I would be breezing.
Outside of owning a server in EU and USA and using a load balancer, what can I do to speed up the experience for US users and get rid of some of that lstency?
I am running Centos 7 with Apache 2.4 and php7 (fast CGI) over a 100mb connection on server in France. The server is dedicated with 16gb ram and a 4 core xeon with 8 threads @2.4ghz.