I received a call from a recruiter in Dublin. They mentioned they were hiring 700 engineers for 2012 in their Menlo Park office. I decided to proceed, even though I wasn't particularly interested. My goal was to observe how their hiring process, which was reputed to be the best in the world at the time, actually worked.

I was interviewed by an engineer from FB who asked me a single question: "How would you implement a cache?"

I responded that I would use a hashmap and began outlining its implementation. I later learned that I should have discussed an LRU cache (the solution for which can be found online).

I was disappointed because the interviewer did not specify that this was what he was looking for. He simply waited, consuming both of our time, while I explained my approach. Within two days, the recruiter informed me that we would not be moving forward, without providing any reason.

It's likely they expect candidates to answer such questions within five minutes. Otherwise, they seem unwilling to consider them further. Their process appears rigid.

I hope other candidates have a more pleasant experience.

They also wanted me to name a situation where I had to make a technical compromise (example: bad code, but which behaves okay for performance).