Beyond Geography: Controlling Traffic Boundaries
Geoproximity routing is a more advanced variant of geographic routing that routes users based on the geographic distance between the user and your resources — and lets you artificially expand or shrink the "catchment area" of each resource using a bias value.
This policy is only available through Route 53 Traffic Flow, the visual policy editor.
How Bias Works
Each resource gets a bias value from -99 to +99:
- Positive bias (+1 to +99): Expands the resource's geographic catchment area. More users get routed to it.
- Negative bias (-1 to -99): Shrinks the catchment area. Fewer users get routed to it.
- Bias = 0: Default behavior — route to the geographically nearest resource.
Concrete example:
You have servers in us-east-1 (Virginia) and us-west-2 (Oregon). By default, users in the central US (say, Kansas) might be split roughly evenly. If you set us-east-1 bias to +50, the boundary shifts westward — users as far as Colorado now get routed to Virginia instead of Oregon.
Use case: You're migrating traffic from one region to another. Instead of an abrupt cutover, you gradually increase the bias of the new region, slowly expanding its catchment area until it handles all traffic.