DNS service 

The DNS service also plays a key role in sending traffic to the appropriate servers. This is normally achieved by using the global traffic manager or a global load balancer, which basically combines the concepts of a load balancer and DNS server. 

Let's take a quick look at how it works. The global load balancer gets a DNS query for a server record it manages. It then takes a look at the load and availability of the server and then sends the DNS response appropriately.

One thing to remember is that the DNS is only queried (after querying it once) when the Time to Live (TTL) expires, hence in order to ensure that the DNS server is queried, we need to lower the TTL. However, as a consequence, the cache is not used for the DNS and there will be a few milliseconds of delay. 

Some public cloud like GCP's DNS services provide global load balancing, but other DNS service providers such as Neustar also provide the service. There are enterprise options such as using F5's Global Traffic Manager that can also be used for this feature.