The Starting a simple sharded environment of two shards and Connecting to a shard from the Mongo shell and performing operations recipes in Chapter 1, Installing and Starting the MongoDB Server, explained how to start a simple two-server shard and then insert data in a collection after choosing a shard key. The data that gets sharded is more technical, where the data chunk is kept to a manageable size by Mongo, by splitting it into multiple chunks and migrating the chunks across shards to keep the chunk distribution even across shards.However, what if we want the sharding to be more domain-oriented? Suppose we have a database for storing postal addresses and we shard based on postal codes, where we know the postal code range of a city. What we can do is tag the shard servers according to the city name as the tag, add the shard range (postal codes), and associate this range with the tag.

This way, we can state which servers can contain the postal...