The 5-Hour CDN
This article touches on "Request Coalescing" which is a super important concept - I've also seen this called "dog-pile prevention" in the past.<p>Varnish has this built in - good to see it's easy to configure with NGINX too.<p>One of my favourite caching proxy tricks is to run a cache with a very short timeout, but with dog-pile prevention baked in.<p>This can be amazing for protecting against sudden unexpected traffic spikes. Even a cache timeout of 5 seconds will provide robust protection against tens of thousands of hits per second, because request coalescing/dog-pile prevention will ensure that your CDN host only sends a request to the origin a maximum of once ever five seconds.<p>I've used this on high traffic sites and seen it robustly absorb any amount of unauthenticated (hence no variety on a per-cookie basis) traffic.