Google Dance is the term coined to describe the index update of the Google search engine. Though there is no fixed date or time for the update, it occurs once every month on an average. And while the update is on, there is significant activity and movement in search results, especially so in Google’s cache of indexed web pages that mark the status of its last crawl. However, the index update is not about switching from one index on to another. Rather, the index update takes several days to get completed and during this time, the old and the new index alternate on Google. In the start, the new index results appear only once in a while but later on the frequency goes up until it stabilizes on a point.

This is why the term ’Google Dance’ is used to refer to the index updates.

Technical Aspects of Google Dance
Google extracts its search results from more than 10,000 simple Linux servers. Index update cannot happen on all these servers simultaneously. The new index has to be updated on the servers one after another

There is a common misconception among webmasters that Google can actually control how the servers with the new index as well as the old index respond to search queries. However, because the Google index is inverse, it becomes a very complicated procedure. The fact is that Google does not control the search results during the index update phase. Rather, the whole movement of search results is because of how Google uses DNS (Domain Name System).

DNS – Domain Name System and Google Dance
All of Google’s ten thousand servers are located across many different data centers across the world. For Google to direct traffic to all the data centers, it should record all the search queries centrally and then transport them to different data centers. However, the process can be highly inefficient. All data centers have their particular IP addresses and the DNS manages the access methodology of these IP addresses.

How does the DNS work?
Data is always transferred between specific IP addresses on the Internet. DNS supplies the information about which domain resolves to which IP address. When you enter a domain name into the address bar of your browser, a local name server contacts the name server of the concerned domain and gets the IP address for the same. The name server then caches the IP address in order to facilitate further communication. This way it the name server would not have to be contacted when the domain is visited again.

Data centers, DNS and Google index update share a crucial relationship. When the Google index update takes place, all the data centers don’t receive the new index simultaneously. Rather, the new index is transferred to the data centers one after the other. Hence, when users search for something on Google, they can either receive results from data centers having the old index or they can get results from the ones having the new index depending on their geographical location. This is the reason for variance of search results during the Google Dance!