Caching is a cruel mistress.

I've probably said that before, but I can't remember whether I've said it before or not, because caching is a cruel mistress.

Those are the two things that will always get you, Caching, DNS and off-by-one errors.

Just invalidate your cache after read access and you are good to go.

Oh my, I read "Catching a cruel mistress"

@djsumdog I came here for this comment.

Caching is easy, invalidation is s bitch.
That is the rule I've always heard.

However there is a second element to it: caching is an attack vector. A lot of people missed that and don't think about it in terms of security.