Generally speaking it’s better to host your server close to your clients. Although a CDN can help for static photos and images and HTML on your website, a CDN won’t help your database query access where it’s tightly coupled to Ajax calls in the browser.
This article provides a tool and a reference to see how to find out which Google Data Centre might be best for you.
The tool is GCP ping. It measures latency from your current location to the close Google DC. You can also gauge comparisons to other parts of the world.
Here is a link to the tool: http://www.gcping.com/
Here is another great resource of where to host if you’re using google: