[goatslacker]

While you're not expected to be an encyclopedia of knowledge about any particular language, framework, or API; having the frequent need to look things up is a red flag because if you're always looking things up you may not move fast enough.

Also, having the "this is not a problem" attitude is a red flag; what else would this person not consider a problem when I hire them?

[enscr]

you might miss out on a lot of bright bulbs if you keep red-flagging them because you think they won't move fast enough.

[goatslacker]

I may; hiring is tough. You only have a few minutes to gauge whether you'll work well with that person or not and bad signals are bad signals. I can't green light all candidates just in case.

It all depends on the tone and the body language and if they're able to continue with guidance.