Before anyone wants to criticize Stack Overflow, consider their server footprints as of 2016 [1]:
4 Microsoft SQL Servers (new hardware for 2 of them)
11 IIS Web Servers (new hardware)
2 Redis Servers (new hardware)
3 Tag Engine servers (new hardware for 2 of the 3)
3 Elasticsearch servers (same)
4 HAProxy Load Balancers (added 2 to support CloudFlare)
2 Networks (each a Nexus 5596 Core + 2232TM Fabric Extenders, upgraded to 10Gbps everywhere)
2 Fortinet 800C Firewalls (replaced Cisco 5525-X ASAs)
2 Cisco ASR-1001 Routers (replaced Cisco 3945 Routers)
2 Cisco ASR-1001-x Routers (new!)
Assuming they aren't lying, this is the entire list of machines needed for a site used by the world's developers. That's no small feat. Many companies whose developers blog about their "best practices" would struggle to achieve 1/10th as much efficiency.
[1] https://nickcraver.com/blog/2016/02/17/stack-overflow-the-ar...