> For Github, are you sure it's even a frontend thing?

Well where do we draw the line here? I'm not even talking about diffs etc.: Just browsing through a repo and looking at single files is noticeable slow. As an end user I don't really care if it's the network request latency or because inefficient DOM rendering, it's not a great UX. For example loading this site here: https://github.com/GoogleCloudPlatform/gsutil/blob/master/te... took 1.26 seconds. And it's like that for any file or folder. Gitlab seems to have a similar initial load time however only once, after that it's faster.