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Stack Overflow uses a WISC stack (削除) via BizSpark (削除ここまで) (we graduated!):

• Operating SystemMicrosoft Windows Server 2019 x64
• Web Server IIS 10
• Database SQL Server 2019 running Microsoft Windows Server 2016 x64
• Language C#

• IDE Visual Studio 2019
• Framework Microsoft .NET 6.0
• Web Framework ASP.NET Core 6.0 with MiniProfiler
• View Engine Razor
• Browser Framework jQuery 1.12.4
• Data Access Layer Entity Framework Core 2.2 and Dapper
• Cache / Additional Data redis 4.0.7 via StackExchange.Redis, with serialization via protobuf-net
• Source Control Git using a GitHub Enterprise instance hosted by GitHub (previously self-hosted GitHub, Mercurial from 2010–2014, Subversion from 2008–2010)
• Compare Tool Beyond Compare 4

• reCAPTCHA
• DotNetOpenAuth
• WMD - Now developed as open source in the project (削除) PageDown (削除ここまで) Stacks Editor
• Highlight.js (was Prettify)
• Google Analytics
• TeamCity
• HAProxy
• MarkdownSharp
• LESS (source)
• MathJax
• Elasticsearch (source)

• WordPress on Linux (Site Blogs) Jekyll (on linux?) (for blog.stackexchange.com )
• WebSocket (for real time updates; custom C# implementation)
• Bandwidth used by Stack Exchange sites
• jQuery Isotope plugin (for the grid-style site list) ^_(Source)

• License Creative Commons Attribution-Share Alike 4.0 for content contributed on or after 2018年05月02日 (UTC); Creative Commons Attribution-Share Alike 3.0 for content contributed between 2011年04月08日 and 2018年05月01日 (UTC); Creative Commons Attribution-Share Alike 2.5 for content contributed before 2011年04月08日 (UTC) (source)
• Standards OpenSearch, Atom
• Host two datacenters:
  • New York: QTS (technically in Jersey City, NJ now). Formerly hosted at Internap and PEER 1.
  • Denver: unknown(formerly hosted at FORTRUST)

Hardware

• 11 Dell R640 IIS web servers (9 shared for all production like SO, two for Meta and development):
  • 2x Intel Xeon Processor Gold 6226 @ 2.7 GHz 12 Core with 24 threads
  • 96 GB RAM
  • Windows Server 2019
  • Two drives
    • 2 Toshiba 480GB SAS SSD (RAID 1)
  • 2x 10 Gbit/s NIC teaming

• Three Dell R720xd database servers (two in New York City, one in Denver, using SQL AlwaysOn Clustering) (Global "Sites" DB & Stack Overflow dedicated):
  • 2x Intel Xeon Processor E5-2680 @ 2.7 GHz
  • 384 GB RAM
  • 21 drives
    • Mirrored Pair for OS
    • 2 Intel P3700 2TB PCIe NVMe RAID1 for databases
    • 24 Intel 710 200GB SSD RAID10 for databases
  • SQL Server 2014 SP1
  • 2x 10 Gbit/s NIC teaming

• Three Dell R730 database servers (two in New York City, one in Denver, using SQL AlwaysOn Clustering) (All other sites, Careers, Area 51, etc.):
  • 2x Intel Xeon Processor X5680 @ 3.33 GHz
  • 768 GB RAM
  • 28 drives
    • Mirrored Pair for OS
    • 2 Intel P3700 2TB PCIe NVMe RAID0 for databases
    • 24 1.2TB 10K RAID10 for large databases
  • SQL Server 2014 SP1
  • 2x 10 Gbit/s NIC teaming

• Two Dell R640 HAProxy servers (direct):
  • 2x Intel Xeon Gold 5218 @ 2.3 GHz
  • 96 GB RAM
  • CentOS 7
  • 2x 10 Gbit/s NIC teaming (internal)
  • 2x 10 Gbit/s NIC teaming (external)

• Two Dell R640 HAProxy servers (CloudFlare):
  • 2x Intel Xeon Gold 5218 @ 2.3 GHz
  • 96 GB RAM
  • CentOS 7
  • 2x 10 Gbit/s NIC teaming (internal)
  • 2x 10 Gbit/s NIC teaming (external)

• 2 Dell R640 Redis servers:
  • 2x Intel Xeon Gold 6244 @ 3.6 GHz
  • 384 GB RAM
  • CentOS 7
  • 2x 10 Gbit/s NIC teaming

• Three Dell R640 Service servers for tag engine/search:
  • 2x Intel Xeon Gold 6244 @ 3.6 GHz
  • 96 GB RAM

• One Dell R620 Backup server running NetBackup (most backups):
  • 2x Intel Xeon Processor E52620 @ 2.0 GHz
  • 16 GB RAM
  • 14 drives
    • Mirrored Pair for OS
    • 12 4TB 10K RPM RAID10 for backups (DAS)
  • 2x 10 Gbit/s NIC teaming

• One Dell R730xd SMB3 Backup server (SQL backups):
  • 2x Intel Xeon Processor E5-2623v3 @ 3.0 GHz
  • 16 GB RAM
  • 30 drives
    • Mirrored Pair for OS
    • 16 6TB 7.2K RPM RAID10 for backups (Internal)
    • 12 4TB 10K RPM RAID10 for backups (DAS)
  • 2x 10 Gbit/s NIC teaming

• Six Dell R640 VMWare ESX servers:
  • 2x Intel Xeon Gold 6240 @ 2.60 GHz
  • 1.5 TB RAM
  • 16x 10 Gbit/s NIC teaming (8x 10 Gbit/s per FX2s)

• 2 Cisco ASR1001-X routers
• 2 ASR1001 Routers
• 2 Fortinet 1100E Firewalls
• 2 Cisco Nexus 5596 Cores in an active/active redundant configuration

1. Stack Overflow's New York Data Center (Server Fault Blog)
2. Designing for Scalability of Management and Fault Tolerance (Server Fault Blog)
3. What Was Stack Overflow Built With?
4. Stack Overflow Server Glamour Shots
5. Technology and SEO profile for stackoverflow.com
6. Stack Overflow and DVCS
7. Stack Overflow Network Configuration
8. https://stackexchange.com/performance

Stack Overflow is built with .NET Core (削除) uses a WISC stack (削除ここまで) (削除) via BizSpark (削除ここまで) (we graduated!):

• Host Google Kubernetes Engine
• Database SQL Server 2022
• Language C#

• IDE Visual Studio 2022, JetBrains Rider, VS Code
• Framework Microsoft .NET 8.0
• Web Framework ASP.NET Core 8.0 with MiniProfiler
• View Engine Razor
• Design FrameworkStacks
• UI FrameworkSvelte
• Browser Framework jQuery 3.7.1
• Data Access Layer Entity Framework Core and Dapper
• Cache / Additional Data Redis viaMemorystore , StackExchange.Redis, with serialization via protobuf-net
• Source Control Git using a GitHub Enterprise instance hosted by GitHub (previously self-hosted GitHub, Mercurial from 2010–2014, Subversion from 2008–2010)
• Compare Tool Beyond Compare 4

• reCAPTCHA
• WMD - Now developed as open source in the project (削除) PageDown (削除ここまで) Stacks Editor
• Highlight.js (was Prettify)
• Google Analytics
• MarkDig
• Azure Event Hub
• Octopus Deploy
• LESS (source)
• MathJax
• Elasticsearch (source)

• WebSocket (for real time updates; custom C# implementation)
• Bandwidth used by Stack Exchange sites
• jQuery Isotope plugin (for the grid-style site list) ^_(Source)

• License Creative Commons Attribution-Share Alike 4.0 for content contributed on or after 2018年05月02日 (UTC); Creative Commons Attribution-Share Alike 3.0 for content contributed between 2011年04月08日 and 2018年05月01日 (UTC); Creative Commons Attribution-Share Alike 2.5 for content contributed before 2011年04月08日 (UTC) (source)
• Standards OpenSearch, Atom
• Host: Google Cloud Platform
  • formerly hosted at QTS (technically in Jersey City, NJ), Internap and PEER 1 in NYC, and in an unknown data center Denver (also formerly hosted at FORTRUST).

1. Stack Overflow's New York Data Center (Server Fault Blog)
2. Designing for Scalability of Management and Fault Tolerance (Server Fault Blog)
3. What Was Stack Overflow Built With?
4. Stack Overflow Server Glamour Shots
5. Technology and SEO profile for stackoverflow.com
6. Stack Overflow and DVCS
7. Stack Overflow Network Configuration
8. https://stackexchange.com/performance
9. Moving the public Stack Overflow sites to the cloud: Part 1

• License Creative Commons Attribution-Share Alike 4.0 for content contributed on or after 2018年05月02日 (UTC); Creative Commons Attribution-Share Alike 3.0 for content contributed between 2011年04月08日 and 2018年05月01日 (UTC); Creative Commons Attribution-Share Alike 2.5 for content contributed before 2011年04月08日 (UTC) (source)
• Standards OpenSearch, Atom
• Host two datacenters:
  • New York: QTS (technically in Jersey City, NJ now). Formerly hosted at Internap and PEER 1.
  • Denver: FORTRUST

• License Creative Commons Attribution-Share Alike 4.0 for content contributed on or after 2018年05月02日 (UTC); Creative Commons Attribution-Share Alike 3.0 for content contributed between 2011年04月08日 and 2018年05月01日 (UTC); Creative Commons Attribution-Share Alike 2.5 for content contributed before 2011年04月08日 (UTC) (source)
• Standards OpenSearch, Atom
• Host two datacenters:
  • New York: QTS (technically in Jersey City, NJ now). Formerly hosted at Internap and PEER 1.
  • Denver: unknown (formerly hosted at FORTRUST)

• reCAPTCHA
• DotNetOpenAuth
• WMD - Now developed as open source in the project PageDown
• Highlight.js (was Prettify)
• Google Analytics
• TeamCity
• HAProxy
• MarkdownSharp
• LESS (source)
• MathJax
• Elasticsearch (source)

• reCAPTCHA
• DotNetOpenAuth
• WMD - Now developed as open source in the project (削除) PageDown (削除ここまで)Stacks Editor
• Highlight.js (was Prettify)
• Google Analytics
• TeamCity
• HAProxy
• MarkdownSharp
• LESS (source)
• MathJax
• Elasticsearch (source)