Why This Puzzle Might Be Harder Than It Appears
Most people will feel that this aspect is very simple: The “People You May Know” feature is so easy to use! You log into an app, browse a few suggested friends, and either dismiss them or ask to add them. But once I started thinking through how such a feature would operate at scale, it became clear that it’s really a far deeper, more involved architectural problem than meets the eye.
At a small scale, a platform can get away with naive heuristics like mutual connections, same company, or same school. These signals are valuable and, surprisingly, can work well in many cases. But problems begin when the network is huge, user behavior is more dynamic, and the platform needs to recommend more relevant people even if the connection between two nodes is not visible from a single rule.