Click the link above to read more from the MOZ blog on their findings in site speed and website backend performance affects overall rankings in search engines.
"Our data shows there is no correlation between "page load time" (either document complete or fully rendered) and ranking on Google’s search results page. This is true not only for generic searches (one or two keywords) but also for "long tail" searches (4 or 5 keywords) as well. We did not see websites with faster page load times ranking higher than websites with slower page load times in any consistent fashion. If Page Load Time is a factor in search engine rankings, it is being lost in the noise of other factors."
"The back-end performance of a website directly impacts search engine ranking. The back end includes the web servers, their network connections, the use of CDNs, and the back-end application and database servers… While we have found that front-end web performance factors ("document complete" and "fully rendered" times) do not directly factor into search engine rankings, it would be a mistake to assume they are not important or that they don’t effect search engine rankings in another way."