If you're entry-level and don't have a network, certs help you get through the HR filter. Once you're mid-level, you can use your network and experience.
This. Simply saying "certifications are bad don't get them" is not universally helpful advice. Some people will definitely face improved career prospects with the right cert(s) depending on their market and level of experience. Not all companies have equally enlightened hiring practices - and not all prospective employees can pick and choose the way some veteran HN members can.
Each moment of silence makes the interviewee feel more tense. Instead of staring at them, why not leave the room while they read through the code and collect their thoughts?
You could even have HR do it. When they arrive, HR hands them the code and instructions. Then, they read it for 15 minutes, until you walk in.
Both of these organizations might be "helpful" if you have a new Internet Explorer vulnerability, but neither will likely help you with a CSRF bug in a bank website.
A better analogy would be if hospitals had doctors do o-chem problems during interviews. Who would do better? The student who just took the class, or the doctor who's been practicing for 10 years?
https://blog.step.com/2016/06/16/more-salaries-twitter-linke...