In normal operations, users are geo DNS routed, also known as geo-routed, to the closest data center. GeoDNS is a DNS service that allows domain names to be resolved to IP addresses based on the location of a user.

In any significant data center outrage, we direct all traffic to a healthy data center.

Several technical challenges must be resolved to achieve a multi-datacenter setup:

1. Traffic redirection: Effective tools are needed to direct traffic to the correct data center. GeoDNS.
2. Data synchronization: Users from different regions could use different local databases or caches. In failover cases, traffic might be routed to a data center where data is unavailable. A common strategy is to replicate data across multiple data centers.
3. Test & deployment: With a multi-datacenter setup, it is important to test your website/application at different locations. Automated deployment tools are vital to keeping services consistent through all data centers.

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