So what’s changed in the last 2 years? Besides replacing some servers and network gear, not much. Here’s a top-level list of hardware that runs the sites today (noting what’s different since 2013):

• 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!)

 

Full article http://nickcraver.com/blog/2016/02/17/stack-overflow-the-architecture-2016-edition/