Can you explain the differences between sharding and replication mechanisms in databases?

Sharding and replication are two different approaches to scaling databases.

Replication is the process of copying data from one server (master) to other servers (replicas). Replicas are usually used to increase availability and distribute read load. Writes typically go to the master, and reads can be performed from replicas. If the master fails, a replica can be promoted to master.

Sharding is the division of data into parts (shards), each stored on a separate server. This allows horizontal scaling of the database by distributing load and data volume across multiple machines. Each record belongs to a specific shard based on a key (e.g., user_id).

Example:

• Replication: one server with a full copy of data + several servers with copies for reading.
• Sharding: 10 servers, each storing 1/10 of the data.

Thus, replication improves fault tolerance and read scaling, while sharding scales write capacity and data volume.