There's no need to ask about anything confidential. Meta published a lot about their internal tech stacks, and they use plenty of open-source stuff. ZippyDB, Interview candidate can also talk about generic stuff, and I can drill on the theory or common practice.

Agreed, but what has it got to do with what you replied to?

I think he's saying that during interviews the candidates were being asked to dive deep into their preceding employers' tech stacks. Which does seem to be asking them to tread in dicey legal waters in a coercive situation.

I see. Always stuggled with this. I think design interview on hypotheticals is better. Or have you used X with follow up questions about X? Probably OK to say we used kubetnetes. But not OK to describe inner workings of a custom controller that speeds up their workloads even if candidate wrote the code.

"couldn't deep dive into their own tech stacks"

Not popular? Who asks someone to break their confidential agreements in front of them, and why would you hire someone who would do that so easily?

What is confidential, exactly? I once had a contract that said that I cannot discuss any technology I used for two years after the contract ends. _Any technology_. So, git. And Postgres and so on.

It's completely normal in tech circles to talk about technology.