I almost always configure Varnish not to cache on Vary Cookie and pair that with some simple changes on the back-end to keep most my pages cacheable. One, don'

I almost always configure Varnish not to cache on Vary Cookie and pair that with some simple changes on the back-end to keep most my pages cacheable. One, don't blindly set Vary Cookie on every single page. Two, when a page only needs minor variation like a username; store the username in a cookie and use JavaScript to display it on the page.