There really are no strong signals, which is why interviewing is relatively painful. Instead, there are a bunch of weak and moderate positive and negative signa

There really are no strong signals, which is why interviewing is relatively painful. Instead, there are a bunch of weak and moderate positive and negative signals, that you have to aggregate into an overall signal. Unfortunately the error bars on those signals are significant, and so usually you only hire on a relatively strong aggregate signal, and even then get it wrong occasionally. Plus, nervousness and comfort with the environment and questions makes the error bars bigger. Depending on the level, but assuming a Senior role, then some stronger (not strong, just stronger) signals are: - ability to code basic solutions in the language of choice - ability to reason about code complexity - ability to get to a solution - ability to explain their reasoning - demonstrate they understand the nuance and complexity of software development - understanding common tools in the domain they are interviewing for (sharding for distributed systems for instance) Same, but on the negative/bad side of things: - arrogance, argumentative, rude (nervousness is totally fine and expected) - one true way-ism - complaining about interviews during an interview - inability to solve basic coding questions - lack of understanding about basic data structures (too many people I've interviewed don't even understand how a hashmap is used)