createStreamGroup  
  Stream groups manage how Amazon GameLift Streams allocates resources and handles concurrent streams, allowing you to effectively manage capacity and costs. Within a stream group, you specify an application to stream, streaming locations and their capacity, and the stream class you want to use when streaming applications to your end-users. A stream class defines the hardware configuration of the compute resources that Amazon GameLift Streams will use when streaming, such as the CPU, GPU, and memory.
Stream capacity represents the number of concurrent streams that can be active at a time. You set stream capacity per location, per stream group. There are two types of capacity, always-on and on-demand:
- Always-on: The streaming capacity that is allocated and ready to handle stream requests without delay. You pay for this capacity whether it's in use or not. Best for quickest time from streaming request to streaming session. Default is 1 (2 for high stream classes) when creating a stream group or adding a location. 
- On-demand: The streaming capacity that Amazon GameLift Streams can allocate in response to stream requests, and then de-allocate when the session has terminated. This offers a cost control measure at the expense of a greater startup time (typically under 5 minutes). Default is 0 when creating a stream group or adding a location. 
Values for capacity must be whole number multiples of the tenancy value of the stream group's stream class.
To adjust the capacity of any ACTIVE stream group, call UpdateStreamGroup.
If the CreateStreamGroup request is successful, Amazon GameLift Streams assigns a unique ID to the stream group resource and sets the status to ACTIVATING. It can take a few minutes for Amazon GameLift Streams to finish creating the stream group while it searches for unallocated compute resources and provisions them. When complete, the stream group status will be ACTIVE and you can start stream sessions by using StartStreamSession. To check the stream group's status, call GetStreamGroup.
Stream groups should be recreated every 3-4 weeks to pick up important service updates and fixes. Stream groups that are older than 180 days can no longer be updated with new application associations. Stream groups expire when they are 365 days old, at which point they can no longer stream sessions. The exact expiration date is indicated by the date value in the ExpiresAt field.