I've been auditing db queries of common/typical request and opening article of Alan Turing in mobile (with warm ParserCache and APCu cache) returns 85 db queries. List of them. Out of which these seem to be related to Growth features (in reverse chronological order):
Wikimedia\Rdbms\SelectQueryBuilder [0.001s] db1135: SELECT actor_name AS `value` FROM `actor` WHERE actor_name IN ('Xaosflux','Xaosflux ep') AND (actor_user != 0) WikiPage::pageData [0.001s] db1135: SELECT page_id,page_namespace,page_title,page_restrictions,page_is_redirect,page_is_new,page_random,page_touched,page_links_updated,page_latest,page_len,page_content_model FROM `page` WHERE page_namespace = 4 AND page_title = 'Growth_Team_features/Mentor_list/Manual' LIMIT 1 Wikimedia\Rdbms\SelectQueryBuilder [0.005s] db1135: SELECT actor_name AS `value` FROM `actor` WHERE actor_name IN ('Sungodtemple','Sdkb','Wugapodes','Nosebagbear','Ahmetlii','Ipigott','Em-mustapha','Bsoyka','Ampimd','Tol','Pelagic','Calliopejen1','Berrely','Bilorv','Elli','DanCherek','ARoseWolf','GenQuest','Eddie891','Qwerfjkl','CaptainEek','Dreamy Jazz','Lajmmoore','Ezlev','Pahunkat','Vukky','EpicPupper','Zoozaz1','TheSandDoctor','Pbsouthwood','Sennecaster','TheresNoTime','Chlod','JavaHurricane','Extraordinary Writ','I dream of horses','Asartea','Blaze Wolf','Ganesha811','Justiyaya','LEvalyn','Michael D. Turnbull','Panini!','Pyrrho the Skeptic','Rotideypoc41352','SCHolar44','Trialpears') AND (actor_user != 0) WikiPage::pageData [0.001s] db1135: SELECT page_id,page_namespace,page_title,page_restrictions,page_is_redirect,page_is_new,page_random,page_touched,page_links_updated,page_latest,page_len,page_content_model FROM `page` WHERE page_namespace = 4 AND page_title = 'Growth_Team_features/Mentor_list' LIMIT 1 (The same happens three times more)
It basically makes four queries three duplicate times (12 times) in every page view. I checked and I haven't enabled growth features in enwiki neither as mentor nor mentee. It needs to at least cache queries inside one request and do not run these queries for people who are not signed on as mentee/mentor.
Here is the XHGui: https://performance.wikimedia.org/xhgui/run/view?id=61c0e37053a0c7a56aa214b3 (callgraph)
I see this WikiPageConfigLoader::load being called 12 times and its cache is a BagOStuff which is just inside request and not persistent (not even inside request unless you make it a singleton) might be related, might not. If it's a config and stays the same per wiki, just use MediaWikiServices::getLocalServerObjectCache