This. We get candidates (HFT) with a CS degree from MIT or something, with 15+ years of industry C++ experience as a senior software engineer, who can't explain

This. We get candidates (HFT) with a CS degree from MIT or something, with 15+ years of industry C++ experience as a senior software engineer, who can't explain the difference between a list and a vector (or when to use each), or give even a ballpark estimate for search/insert/remove times for a basic BST. At the same time, there are candidates who are technically good at coding, but terrible problem solvers. We do use whiteboards for the interview, but more as a conversation starter for the algorithmic design, and don't expect compile-able code. In fact, when I interviewed here a year ago, I didn't touch the whiteboard, and we just talked about the design, tradeoffs, wrinkles/edge cases, etc. It is usually a pretty organic process. If we get into it and question their coding ability, we might ask a few basic questions, like how do you declare an array or vector in C++. Do you use std::algorithm? Then possibly into C++14 territory. It depends on the position. On the other hand, if they breeze through some basic coding questions, it quickly turns into a discussion and feeling the candidate out in terms of fit. But if we get a senior SE come in, and we talk about previous projects and we get "I fixed bugs, reduced memory usage, and saved $X million dollars" that is a big red flag.