Varnish

See this for installation instructions and Cloudflare varnish config:

http://www.htpcguides.com/configure-wordpress-varnish-4-cache-with-apache-or-nginx/

See this for actual Varnish 4.0 config with Mediawiki:

https://www.mediawiki.org/wiki/Manual:Varnish_caching#Configuring_Varnish_4.x

Notice that if you're using SSL, Varnish isn't able to process SSL encrypted data. However, Nginx can function both as the PHP-FPM backend of varnish and an SSL decrypting frontend to varnish.

See the guide below to redirect Varnish HTTP to HTTPS.

https://www.smashingmagazine.com/2015/09/https-everywhere-with-nginx-varnish-apache/