Google’s John Mueller said that when it comes to Google measuring speed with the upcoming Google Page Experience and Core Web Vitals metrics, that sometimes individual slow URLs can potentially impact other faster URLs if Google cannot determine the speed of those faster URLs and those URL structures look similar.

In short, he said that Google does try to be as granular as possible with most of the ranking metrics it uses. But when it comes to the data around how fast a URL is, often Google’s data is not there. So it has to use the data of the site’s aggregate URLs on other URLs of your site. Now, he did say that if you have a subdomain or subfolder that is slow and the rest of the site is fast, then Google is more likely to just treat that section of the site as slow and that won’t impact the rest of your site. But it depends. 🙂

Here is the video embed on how he answered this starting at the 14:33 mark into the video:

Here is the transcript:

Forum discussion at YouTube Community.