GeoDNS and Latency-Based Routing: Serving Users the Nearest Server

GeoDNS returns different DNS answers depending on where the query comes from, so a visitor is directed to the server nearest them — cutting latency for a global audience. Latency-based routing is a close cousin that picks the target with the lowest measured round-trip time. Both are powerful, with caveats worth understanding.

How GeoDNS works

An ordinary DNS name returns the same answer to everyone. A GeoDNS-enabled authoritative server instead looks at the location of the incoming query and returns a region-specific answer — pointing a European visitor to a European server and an Asian visitor to an Asian one. The result is shorter network paths and faster responses.

Latency-based routing

Rather than pure geography, latency-based routing directs users to whichever endpoint currently has the lowest latency to them — which usually correlates with distance but accounts for real network conditions. It is common on managed DNS platforms that measure performance continuously.

The big caveat: whose location?

GeoDNS sees the resolver's location, not necessarily the user's. If someone uses a distant public resolver, they may be routed based on the resolver's position, not their own. The fix is EDNS Client Subnet (ECS), an extension that passes a portion of the client's network to the authoritative server so it can decide based on the actual user. Not every resolver sends ECS, so GeoDNS is very good but not perfect.

GeoDNS vs anycast vs CDN

• GeoDNS — returns different answers by location.
• Anycast — one IP, routed to the nearest node by the network.
• CDN — caches and serves your content near users.

They are complementary: GeoDNS or a CDN can direct users to nearby infrastructure, while anycast keeps the DNS layer itself fast and resilient.

Frequently asked questions

Does GeoDNS see the user's location or the resolver's?

By default the resolver's, which is usually close to the user but not always. EDNS Client Subnet improves this by passing part of the client's network, letting the authoritative server route based on the real user when the resolver supports it.

Is GeoDNS the same as a CDN?

No. GeoDNS routes DNS answers by location; a CDN caches your content near users. You can use GeoDNS to steer traffic between regional servers, or a CDN to serve content — and often both together.

When do I need GeoDNS?

When you run servers in multiple regions and want to send each visitor to the nearest one. For a single-region site, a CDN for content usually delivers the global speed benefit more simply.