The Mechanics of Geo-Routing

How does Netflix know to serve you from a server in your city? How does Amazon show you local currency?

DNS-Based Geo-Routing

This is the "classic" method. When your browser queries api.example.com, the DNS server looks at your IP address (or the IP of your ISP's resolver).

It consults a GeoIP database (like MaxMind) mapping IPs to Latitude/Longitude. It then calculates the distance to your server endpoints and returns the IP of the closest one.

The Problem with DNS routing

It depends on the TTL (Time To Live). If a server goes down, clients might still try to connect to it for minutes until the cache expires. Also, public DNS resolvers (like 8.8.8.8) can obscure the user's true location unless EDNS0 Client Subnet is supported.

Anycast Routing

Anycast is the "modern" method used by CDNs. You announce the Same IP Address from 100 locations. The internet's BGP routing table naturally directs the user to the closest location.