The Halloween Server Shadow: Spot the Impossible One

The Halloween server shadow puzzle has three servers and one impossible cable. Which shadow does not belong?

I promised myself that a Sunday puzzle in the week before Halloween could be a little theatrical. So the servers have gone into the dark, and the cables are casting long, suspicious shadows. Nothing is broken in this server room. The drama is in one mismatched outline.

Look at cabinets A, B and C across the top. Each has a short cable that bends away from its side. The shapes beneath are their supposed shadows. Which shadow could not have come from the cabinet directly above it? The racks have the same plain body, so follow the little cable and ignore the three horizontal slots on the front.

This is a matching puzzle, not a test of how real light would fall in a data centre. Treat each shadow as a flat silhouette of the rack above it. One cable changes sides. If you see it quickly, you have earned the rest of your Sunday.

The Halloween Server Shadow Answer

B is the impostor. The cable on cabinet B bends to the left. Its shadow bends to the right. A and C keep their cables on the same side in their matching silhouettes. You can check by covering the other two columns and looking only at the little protrusion.

A silhouette removes colour, labels and surface detail. It leaves shape. That makes it a nice way to notice the feature that matters, and it also shows how much noise we normally carry into a comparison.

When I review a query plan, I sometimes do the same thing mentally. I hide the colours and friendly icons, then ask what the operators and arrows actually connect. A beautiful plan picture can still tell a wrong story if I misread one direction.

No server was harmed to make this shadow. The only victim is my confidence when I first glanced at B and said it looked fine. That is probably an appropriate Halloween ending for a database administrator.

Published by Pinal Dave on SQLAuthority. More of my work at pinaldave.com.