Anycast ip.

You have a sole ip address. All traffix routed to nearest PoP. The PoP makes the call on where and how to route the request.

Lookup google front end (GFE) whitepaper. Or thd google cloud global load balancer

That front end server that lives in the PoP can also inspect the http packets for layer 7 load balancing.

https://cloud.google.com/load-balancing/docs/load-balancing-...

Added to my comment, but basically S3 is not a CDN - it doesn't have PoPs/anycast.

They _do_ use anycast and PoPs for the DNS services though. So that's basically how they handle the routing for buckets - but relies entirely on having separate subdomains.

What you're saying is correct for Cloudfront though.

With SDN the PoP would only need to receive the TCP request and proxy TCP acks.

Raw data could flow from a different PoP that's closer to DC.

Aka user->Closest PoP-> backhaul fiber -> dc->user

Presumably Amazon has PoPs for CloudFront; why couldn't S3 share the same infrastructure?

They could do that, but they have absolutely no incentive to do so - all it would do is cost them more. S3 isn't a CDN and isn't designed to work like one.

It means two hops not one. S3 gets can be cached but then you have a whole host off issues. Better to get to the origin.