Member-only story
Global Traffic Routing: Latency, Residency, and Regional Failover
At 10:03 AM, your application is healthy in two regions. At 10:04 AM, one region starts returning errors. Your global routing system detects the problem and redirects traffic to the other region.
The dashboard turns green.
Then the database connection pool in the surviving region saturates. Some users see stale data. Others cannot log in because their sessions depend on the failed region. A subset of customers is routed outside its permitted data boundary.
The routing system did exactly what it was configured to do: move traffic away from an unhealthy destination.
The problem is that a healthy destination is not necessarily a safe destination.
Global traffic routing involves much more than choosing the geographically closest server. A production design must account for latency, regional capacity, health checks, DNS caching, data consistency, customer residency requirements, and the behavior of the entire system during failure and recovery.
This article explains how to make those decisions, how the main routing approaches differ, and why regional failover must be designed as an application-level capability rather than treated as a DNS configuration.
