The Fly Platform gets close to users by running applications in datacenters close to users. These datacenters are identified by region.
The platform works out which region an application should be running in based on the incoming connection from a client. It then starts the application in that region and completes the connection.
This means that an application does not need to know which region it is running in.
There are a set of Fly capabilities available to applications, such as region-local Redis databases, that are tied to a region.
When an application is started, a three character value is set in the environment variable
FLY_REGION reflecting the region it is running in.
|Region ID||Region Location|
|atl||Atlanta, Georgia (US)|
|dfw||Dallas, Texas (US)|
|ewr||Parsippany, NJ (US)|
|iad||Ashburn, Virginia (US)|
|lax||Los Angeles, California (US)|
|ord||Chicago, Illinois (US)|
|sea||Seattle, Washington (US)|
|sjc||Sunnyvale, California (US)|
FLY_REGION is just one of the range of Runtime Enviroment information available to applications.