I answered the hash table question with the following: it's a one to one mapping of a unique key object to a value object. They asked how it finds the value that corresponds to a key. I said it uses a hash function to find an index into a list of values; more or less depending on the implementation. They asked how hash collisions are dealt with. I could not recall how this is resolved and told them so. They were not impressed. They explained that these difficult questions were designed to "find your edges". Why a web dev needs to know the low level implementation details of a hash table or the linux scheduler is beyond me. It felt like programmer elitism more than determining ones general skill level. Perhaps it is a technique used to low ball you into a lower salary. I discussed this interview process with other experienced software professionals. It sounds like it was a more difficult and stressful process to go through than is typical. The pressure of this interview caused me to perform much worse than I could have but I am not resentful regarding their decision.