# High Availability and Scale Deployment considerations

For Production environments, ensure that all components and its dependencies are deployed in a High Availability architecture. These includes:

* API Instances:
  * Deploy with a Load Balancing front end
  * Have at least 2 machine instances running the API services
  * You can configure Load Balancing with several methods
    * IIS Web Server with ARR as mentioned [here](https://docs.microsoft.com/en-us/iis/extensions/configuring-application-request-routing-arr/http-load-balancing-using-application-request-routing)
    * Use Windows Server [Network Load Balancing](https://docs.microsoft.com/en-us/windows-server/networking/technologies/network-load-balancing) 
    * Or use dedicated load balancers like F5.
  * Though the API calls are stateless, in order to give a better experience and performance, configure load balancing with sticky sessions (requests from the same client/IP during the same session goes to the same backend API node).
* Agent Services (Windows NT Service)
  * Install Agent Service on the first machine, configure and ensure its running. The first machine will become the primary (master).
  * Install Agent Service on a second machine, configure and ensure its running. The second machine will register itself as a secondary and will take over as primary (master) if the first agent stopped.
* SQL Server 
  * Deploy with Always ON / Fail over cluster.
  * Read more on SQL Server Business continuity overview [here](https://docs.microsoft.com/en-us/sql/database-engine/sql-server-business-continuity-dr?view=sql-server-ver15).


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