[djb_hackernews]

Yea I must be missing something here.

If you have k=2 stream managers you have 1 connection, not 4 . Even if the connections weren't bidirectional you'd have 2 connections.

[bmm6o]

Parent is talking big-O and so is ignoring that it isn't exactly k^2. Depending on how you count (do 2 nodes require 2 connections or 1 bi-directional connection) it's k(k-1).

[Horusiath]

it's (k-1)^2 actually - each to each except self.