When I worked at Apple they made it abundantly clear that EVERYTHING was under NDA. Even things like “what version of the standard library do you use”. Or “what are computers for”. And that any minuscule transgression of the NDA would result in me
Being immediately deported, divorced, and likely put in front of a firing squad.
That can’t tell you that you can’t explain how Kubernetes works or NGINX or the JVM. Any one of those things would be perfectly acceptable as a starting point.