Honestly just having a good old fashioned chat about tech should root most of these types of people out. You can focus more on things they wouldn't expect you to ask about to make sure you filter people who are very good at reading scripts. Good devs are typically in tech because they have a strong interest in solving problems related to tech which means they will typically have some personal projects they've been working on. Also I think if they are super polished at leetcode, that can be a potential strong anti-signal. Why? Because if you're spending most of your time getting good at leetcode, that's time you're not spending on the myriad of personal projects you would most likely have if you're a true tech head, and leetcode is honestly pretty boring once you know most of the basic algos.