MongoDB/Sharding

Sharding distributes data across multiple machines instead of keeping an entire dataset on a single server. MongoDB uses a shard key to decide how documents are distributed, allowing both storage and workload to scale horizontally.

Choosing the shard key is one of the most important decisions in a sharded system. A poor key can create uneven data distribution or concentrate traffic on a small part of the cluster, while a good key helps distribute both data and operations across shards.