How traffic is routed is not always logical, and highly dependent on the upstream provider you are using. This means that a request from Hong Kong to Tokyo might actually route through San Jose, instead of the much closer Tokyo edge node.
There are also instances where one global rule, might not make sense for a specific use. For example, you might be leveraging the Geo-Based feature with an edge node in the Philippines for the Asian area of operation. A user in Hawaii might technically be in the Asian AO, but the San Diego server might be physically closer, or the San Jose server might be responding fastest.
Proximity routing helps tackle this problem by allowing a network admin to dynamically respond to a request according to the response times the network is seeing.
Said simply, if a user is in Hawaii and they are receiving faster responses from a server from San Jose, vs their logical location in Asia, this feature will allow the network to dynamically adjust traffic to respond according to the closest, fastest, edge node. This ensures that your users are constantly getting optimal global performance.
We do this by leveraging enhanced records inside the Authoritative Zone for a Domain. We recognize these enhanced records as part of our Smart Routing feature set.