Santa uses MongoDB with geospatial indexes to manage his database of "Dear Santa" letters and present locations, allowing him to efficiently deliver gifts to 6 billion people in one night. He maintains a record for each person, including their location, address, and zip code, which enables him to find presents to be delivered in specific cities or regions. Santa uses geospatial indexes to optimize his delivery algorithm, which involves finding the nearest presents to deliver once he reaches a certain city. The indexes also allow him to use spatial queries, such as the `$near` operator, to get a list of presents to be delivered based on their distance from the center of the city or a specific point. Additionally, Santa uses polygons to define the boundaries of cities and optimize his delivery routes. By leveraging MongoDB's geospatial capabilities, Santa is able to deliver gifts efficiently while minimizing errors and ensuring that everyone receives their desired presents.