Summarizing and summarizing the official facts, research and opinions, we can say that the following parameters of the site affect its effectiveness (and the effectiveness of its promotion):
Directly affects the response time of the server. Given the network delays, it should be no more than 300ms. Even a slight increase in its negative impact on the number of pages and position in the issue (negative effect of 10-30%).
Directly affects the availability of the site (including the number of pages with server errors). Nobody measured the negative effect here, but by analogy with the server response time (reducing the frequency of site visits by the search robot), losses of 5-15% are possible in positions, reach and visitors.
The total load time of the pages of the site affects indirectly through behavioral factors The direct effect is difficult to estimate, it ranges from 5% to 20% with a decrease in site loading time to 4 seconds. If your site takes less than 7 seconds to load, then the great effect of acceleration is difficult to expect.
P.S. and for a snack – video from TopExpert, about the ranking factors that take into account the speed