Disclaimer: We write distributed systems software.
The question I always ask of programmers is this:
You have n=10 computers in a cluster. Every one of them is connected to every other (but not to itself), using bidirectional TCP connections. How many TCP connections total in the cluster?
If they can't figure it out, I change it to n=4, then n=3 and ask them to work their way up from there.
The question I always ask of programmers is this:
You have n=10 computers in a cluster. Every one of them is connected to every other (but not to itself), using bidirectional TCP connections. How many TCP connections total in the cluster?
If they can't figure it out, I change it to n=4, then n=3 and ask them to work their way up from there.