If you serve static documents a single powerful server can easily handle 40,000 requests per second (I think now it's more like 100,000 queries per second for Google, BTW). So I don't think the web server is the bottleneck here, it's the complex backend system that answers the queries. Regarding Google scale, I think you can achieve that with almost any software stack, as the scaling doesn't happen on the level of the web server. You have mechanisms like anycast, DNS load balancing etc. that can distribute load to multiple data centers (DC), and within a data center you can use load balancing on layer 4 (TCP/UDP) to distribute incoming traffic to a fleet of different servers. I guess at that scale the consideration which stack to use is more driven by overall cost, i.e. if you can reduce your server count by 90 % by switching to a more performant stack that will dictate your technology choice. Also, under really heavy load I'd say it's more likely that other central components in your DC like your core switch will be the bottleneck, as you can't really scale those horizontally.