I'm just finishing up my first D8 development and looking to refine the performance of the site.
Surprisingly I'm seeing some pretty scary processing time of twig templates by webprofiler. An uncached page has >7000ms of twig processing which is mostly consumed by views-view.html.twig, views-view-unformatted.html.twig and a node template. The best cached performance still sees twig consuming 500ms and a page load is around 1300-1600ms.
With BigPipe turned on I can achieve 400ms twig, page load of 1000ms.
This is on an idle 4 core server.