There is a layer in my database called 1 . Somebody created it, presumably by accident, and it sat there for months looking harmless. It was the only layer in the system that never served a single tile, and nobody noticed, because it was empty anyway.
Source: [Dev.to](https://dev.to/srdjan_poppovic/one-view-per-layer-four-sharp-edges-i-found-in-my-own-code-23e8)