Every ship in the world is constantly shouting its name into the void. Its position, its heading, its speed, its destination — broadcast every few seconds via radio, picked up by satellites and shore stations, and funneled into databases that try to make sense of it all. At VesselAPI, we run one of those databases. And for the first year of our existence, we ran it on MongoDB. This is the story of why we stopped. It's also a story about hexagons and a single mismatched struct tag that quietly broke an entire data pipeline. The Shape of the Problem AIS — the Automatic Identification System — is the backbone of maritime surveillance. Most commercial vessels are legally required to carry a transponder that broadcasts their identity and position — SOLAS mandates it for ships of 300 gross tonnage and upwards on international voyages, and many flag states extend the requirement further. The result is a firehose: at peak hours, we ingest roughly 700,000 position reports every sixty minutes.…