google.com, update.microsoft.com, and other services which handle astonishingly high aggregate bandwidth do much of their magic via DNS.
BGP Anycast routing is used to announce the IP address of their DNS servers from multiple points around the world. Each DNS server is configured to resolve google.com to IP addresses within a data center which is geographically close. So this is the first level of load balancing, based geographically.
Next, though a DNS query for google.com will return only a small number of IP addresses, the DNS server rapidly cycles through a large range of addresses in its responses. Each client requesting google.com will get a particular answer and will be allowed to cache that answer for a while, but the next client will get a different IP address. So this is the second level of load balancing.
Third, they use traditional server load balancers to map sessions to a single IP address to multiple backend servers. So this is a third level of load balancing.