We were having an internal discussion regarding what specific signal Google is looking for regarding Site Speed. My understanding was that Google primarily used Time To First Byte (TTFB) as its signal of Site Speed. My colleague argued that this is not part of Google's PageSpeed Insights (https://developers.google.com/speed/pagespeed/insights/) and therefore was unlikely to be the primary signal. Who is right? Is TTFB the primary signal or the score on PageSpeed Insights?
