The longest and hardest interview in my 14+ years career. Mostly they test your memory. If you somehow know at the same time about CSS3 Transitions, why JavaScript "var a=b=3;" is tricky, what is PHP "realpath" function and why "substr" is generally not good. If you know the structure of "inodes" in Unix systems, 3 differences between InnoDB and MyISAM; about "$$" in bash, about Etags and browser caching strategies as well as can answer other 50-70 technical questions, - then maybe you are good for them. The whole interview process took me 3 hours.