CDN
Also called Content delivery network, Edge
A network of servers around the world that keep copies of your files close to users. Requests go to the nearest one, and only a miss has to travel on to your real server, which is called the origin.
It's the only real fix for distance, and it takes load off your server. It also means a mistake in your cache headers is now served to the world. Personal pages must never be shared, so have the agent prove it with the response headers.
Say it to your agent
“Run curl -I on /assets/app.js twice and show me CF-Cache-Status, which should say HIT the second time. Give /account Cache-Control: private, no-store, and show me that header too. Tell me what happens to our server when the cache is purged.”