I have not read a reddit devblog or anything like that. My guess is they are doing some kind of caching of posts via elasticsearch/redis or something similar. It must depend on the privacy settings of a sub.
So when 1000 subs go private, they potentially had to update hundreds of millions of comments.
So when 1000 subs go private, they potentially had to update hundreds of millions of comments.
Anyone else have a theory?