How to Reduce Server Response Time in Page Speed Insights

Hello

I always believe long web server response times delay page loading speeds. When i tested webpages in Google page speed insights, the tool expects my server to respond quickly to resource requests to ensure a quick page load time. My page score was 90 and server response time 0.39 sec, But every time the tool is highlighting the server response time under "should fix"

My question is what is the best server response time i need to get that? so the tool consider not to include my server response time in "should fix" and "consider fixing" sections

It is 200ms (.2 seconds) developers.google.com/speed/docs/insights/Server