Beyond Nearest
Anycast sends users to a nearby POP, but applications often need to steer traffic by deliberate policy, not just proximity. Geo routing and traffic steering add that control.
Geo Based Decisions
A steering layer, often at DNS or the edge, maps a user to a region using location.
- Latency: send to the region with the lowest measured delay.
- Compliance: keep certain users data within a legal boundary.
- Locale: serve a region specific site or pricing.
The decision can use the resolver location or, more precisely, the client address at the edge.
Steering Policies
Beyond raw geography, operators apply policies that shape where traffic lands.
- Weighted: split traffic across regions by share for gradual rollouts.
- Failover: route to a backup region when the primary is unhealthy.
- Capacity aware: shift load away from a saturated region.
Health checks feed these decisions so steering reacts to real conditions.
Pitfalls
- Resolver mismatch: DNS sees the resolver, not the user, so a distant resolver can misplace a user unless client subnet hints are passed.
- Caching: DNS answers are cached, so steering changes propagate only as records expire.
- Stickiness: moving a user mid session can break state, so steering must respect existing affinity.
Key idea
Geo routing and steering direct users to a region using location plus policies for latency, compliance, weighting, and failover, while watching for resolver mismatch, DNS caching, and session stickiness.