Get node info from within admin endpoint


in an admin endpoint I'd like to access a node's property which is a password field named "apikey". I've followed the guideline from here:

The goal is to serve a list of strings, which come from the api for which the key from the "apikey" field is for.

So now I'm at the point where I'd like to access the node's apikey field, but don't know how to open the node for inspecting this value.

Is that doable or is there a better course of action?