What is Shard

Sharding is physically breaking large data into smaller pieces (shards) of data. A database shard is a horizontal partition in a database or search engine. Each individual partition is referred to as a shard or database shard. Sharding is an application-managed scaling technique using many (hundreds/thousands of) independent databases. Vertical scaling is limited by cost and implementation since it is difficult to scale in the cloud vertically. Horizontal partitioning is a database design principle whereby rows of a database table are held separately, rather than being split into. Each partition forms part of a shard, which may in turn be located on a separate database server or physical location. Features of sharding are as follows: 1) Data is split into multiple databases (shards); 2) Each database holds a subset (either range or hash) of the data; 3) Split the shards as data volume or access grows; 4) Shards are replicated for availability and scalability; and 5) Sharding is the dominant approach for scaling massive websites. Sharding is used in custom applications that require extreme scalability and are willing to make a number of tradeoffs to achieve it.

NoSQL Databases

Ganesh Chandra Deka (Ministry of Labour and Employment, India)