Happens both logged in and logged out. Read API requests to Flow topics like https://test.wikipedia.org/w/api.php?action=flow&submodule=view-topic-history&page=Topic:Spurbjt59b0sypf1&vthformat=wikitext are also slow, also around 22s. mediawiki.org is not affected, but it hasn't been updated to wmf1 yet.
Sometimes, it seems like loading both loading the topics and edit interface on nowiki is awfully slow. I have not timed it, so I don't know how slow it really is. I would guess it is about half a minute. It is somewhat hisenbug-like.
Reopen the bug?
@jeblad Can you please give specific pages that load slow? Yesterday it was noticeably slower than usual on testwiki but not too slow.
I was checking today testwiki and nowiki and it seemed that pages successfully load between 3.07s to 1.35 s ; posting Replies on Flow board or opening for Edit is also normal.
And for the issue, it's better to open a new bug for Regression on 1.28.0-wmf.6 with the tag Performance.