Yes the Java async messaging stuff required some pretty deep understanding, especially ironing out a couple of deadlock bugs (ironically drawing a diagram in whiteboard fox helped me understand the deadlocks: https://s1.whiteboardfox.com/s/420876221780898a.png)
I would have much preferred a solid framework or library. Maybe I didn't spend enough time researching the alternatives to writing it myself.
But then again I wonder if a library would have had the low-level flexibility I needed. For example, I found that one of the most frustrating things when using whiteboard fox was that your internet connection would go down and you wouldn't know about it. So you would not realise that there was a problem and think that the other person had simply stopped drawing. My solution was to add a 5-second heartbeat so that the browser could display a 'disconnected' message when it didn't get the heartbeat. Would a high-level library allow me the option of such a heartbeat?
I agree this is a great start. This is a good example of how solid implementation is almost always much more important then "newer/better technologies".
Its a bit of a tangent, but it makes me think how "feature focused" people are when hiring, do you know x/y/z with domain experience in q?
The right questions are, is this candidate a intelligent, a fast learner, reliable, have a track record of producing?
