Invalidating quickly is the main problem with caching on a CDN. We use an async worker via Redis pubsub to call for expiration on individual files locally on pr

Invalidating quickly is the main problem with caching on a CDN. We use an async worker via Redis pubsub to call for expiration on individual files locally on proxy servers we run. I'm looking at using NSQ for this in the future. One interesting solution is to just use an HTTP hit to expire a cache, which you can see a flavor of in our nginx config file. Nginx in effect becomes it's own cache SoA. We needed a special nginx module to make that work, default nginx only lets you expire the entire cache. Fastly probably has something similar. You've really got to do this within 5 seconds or your user is going to get pissed off waiting for it every time they save/reload the page. The big problem with passing caching to third party CDNs is that they need to be able to handle your SSL certs inline to request static files you don't need to change the URL of (because then you would be changing the published content which you don't control), and supports wildcards. In effect you're doing what Cloudflare does. I'd use Cloudflare in a minute for this, but wildcards require their commercial plan and we can't afford it ($6k/mo). Also we would need fine-grained cache expire. If Fastly does this and is priced in our range, maybe we should talk to them. :)