MongoDB Atlas's Global Clusters are a distributed architecture that uses a location-based sharding key to route queries and write requests to the nearest replica set, reducing latency for users across the globe. By prefixing the sharding key with a location code, MongoDB can create a region-based map of the world, allowing users to select regions for their replica sets and manage latency and load accordingly. This feature is unique to MongoDB Atlas and provides a simple way to deploy a globally distributed network of databases, making it an obvious option for running MongoDB in the cloud.