Explanation/Reference:
The KVStore is a collection of Storage Nodes which host a set of Replication Nodes. Data is spread across the Replication Nodes.
Each shard contains one or more partitions. Key-value pairs in the store are organized according to the key. Keys, in turn, are assigned to a partition. Once a key is placed in a partition, it cannot be moved to a different partition. Oracle NoSQL Database automatically assigns keys evenly across all the available partitions.
Note: At a very high level, a Replication Node can be thought of as a single database which contains key- value pairs.
Replication Nodes are organized into shards. A shard contains a single Replication Node which is responsible for performing database writes, and which copies those writes to the other Replication Nodes in the shard.
References: https://docs.oracle.com/cd/E26161_02/html/GettingStartedGuide/introduction.html