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TeamCity builds then copies to each web tier via a powershell script. The steps for each server are:

• Tell HAProxy to take the server out of rotation via a POST
• Delay to let IIS finish current requests (~5 sec)
• Stop the website (via the same PSSession for all the following)
• Robocopy files
• Start the website
• Re-enable in HAProxy via another POST TeamCity

The UI has message inbox that is sent a message when you get a new badge, receive a message, significant event, etc. Done using WebSockets and is powered by redis. Redis has 2 slaves, SQL has 2 replicas, tag engine has 3 nodes, elastic has 3 nodes - any other service has high availability as well (and exists in both data centers). Redis