Google posted last summer that "page speed" will impact the search result rankings also on mobile devices. But I think there is a little confusion about the term "page speed".
The test tool which Google offers is called "Page Speed Insights". Many people we are talking with, are thinking that the overall score of this tool for a particular site for example Desktop: 46/100 and Mobile: 45/100 is used for the ranking algorithm.
BUT I found a very interesting article in German language which states that only the TTFB (time to first byte) value is used and this should be optimized not all suggestions which "Page Speed Insights", further called PSI offers. Here is the link to the German article: https://raidboxes.de/google-pagespeed-insights-nytimes/#comment-405
In short terms it says that a very large site in this case "The New York Times" has a low overall score of Mobile:41 and Desktop:45. As they are used to sell reader memberships they should offer a great user experience. So, they should optimize their site. But when I call this site it is amazing fast. The overall PSI score does not reflect this behaviour. But when I believe this article the TTFB for this site is perfect. Also when I call it here from Austria it states 0.881sec.
I really like to know on which value we should focus our work for optimization not to fall in the ranking. Because as many of you already said it is not useful to implement all suggestions from the PSI site for one domain.
So, it would be real if you could clarify things here or post links to official posts from Google. What I found about this, Google always is talking about "page speed" but what exactly is this?