What is the key difference between Replication and Sharding?

Answer:

a) Replication takes the same data and copies it over multiple nodes. Sharding puts different data on different nodes

b) Sharding is particularly valuable for performance because it can improve both read and write performance. Using replication, particularly with caching, can greatly improve read performance but does little for applications that have a lot of writes. Sharding provides a way to horizontally scale writes.