The big killer here isn't just round trip time, it's the RTT compounded with the 14KB limit from TCP before it stops blindly sending data and compounded with extra resources that have to be fetched in a chain. If you keep the size of the response under 14KB and don't have render-blocking links to CSS and JS a page will be pretty fast; the moment it's any bigger the time before page load will double. I'm happy waiting about 300ms for a page served from the east coast of the US to load, but 600ms becomes noticeable and anything more - JS which loads more JS which loads JSON and blocks rendering until it's done, for example - starts to be excruciating.
The big killer here isn't just round trip time, it's the RTT compounded with the 14KB limit from TCP before it stops blindly sending data and compounded with extra resources that have to be fetched in a chain. If you keep the size of the response under 14KB and don't have render-blocking links to CSS and JS a page will be pretty fast; the moment it's any bigger the time before page load will double. I'm happy waiting about 300ms for a page served from the east coast of the US to load, but 600ms becomes noticeable and anything more - JS which loads more JS which loads JSON and blocks rendering until it's done, for example - starts to be excruciating.