https://github.com/blog/1766-proxying-user-images
They refer to it as "proxying", but they also call out that it proxies using their CDN, which seems to imply there isn't a 1:1 relationship between user requests and hits on the backend server
Edit: Would it not be possible/better to just serve the SVG image direct from nginx? There is a LUA plugin, or even some direct redis stuff you could use.
edit: and regarding lua or nginx redis2, yes you could certainly do that. I happen to like the asynchronous nature of incrementing hit counters outside of the request cycle and just using nginx to serve the static badge files. But yeah there are a bunch of ways to do this.