Page https://en.wikipedia.org/w/index.php?title=European_Union&type=revision&diff=938561921&oldid=938557616 became quite popular due to a reddit comment, and we have noticed that it takes about 15s to render
Profiling data: https://phabricator.wikimedia.org/P10297
Both are running 1.35.0-wmf.16 at the moment.