FML, something that’s changed between Node 12.16.2 and 18.16.0 has made the OCSP stapling library I’m using¹ 1000× slower (~4ms vs ~4s per request).
At least I know where the issue is… Tomorrow, I dig into the library to try and narrow it down further.
(The network graph in Firefox was useful as it showed that the problem was with the TLS Setup. And 0x² and its flame graphs helped me narrow it down further.)
¹ https://github.com/indutny/ocsp#ocsp-apis-for-nodejs-
² https://github.com/davidmarkclements/0x#readme