If you want an easy speed up and you use a modern version of nginx, which you should for many reasons but chiefly performance and security.

Add these lines to your nginx config file:

    # Only support HTTPS and enable http2 
    # which will allow you to multiplex requests.
    # In a separate config do a 301 from normal HTTP
    # for all paths / subdomains.
    listen 443 ssl http2 default_server;
    listen [::]:443 ssl http2 default_server;

    # Make TCP send multiple buffers as individual packets.                                                                                   
    tcp_nodelay on;

    # Send half empty (or half full) packets.                                                                                                 
    tcp_nopush  on;

It reduced our page load time by around 75%, and more for people accessing the site from the other side of the world.