In this recipe, we will be looking at MongoDB's shard zones. A zone is essentially a group of shards based on a specific set of tags. Zones can help the distribution of chunks based on tags, across shards. All reads and writes, pertaining to documents within a zone, are performed on shards matching that zone. There can be various scenarios where zone based sharded clusters can prove to be highly useful. For example:
An application that is geographically distributed would require that the frontend, as well as the data store, is close to the user
The application has a multi-tier hardware architecture such that certain records are fetched from a higher tier (low latency) hardware whereas others could be fetched from a low tier (high latency inducing) hardware