DocDB sharding layer

This section describes how sharding works in DocDB. A distributed SQL database needs to automatically split the data in a table and distribute it across nodes. This is known as data sharding and it can be achieved through different strategies, each with its own tradeoffs.

Data sharding helps in scalability and geo-distribution by horizontally partitioning data. A SQL table is decomposed into multiple sets of rows according to a specific sharding strategy. Each of these sets of rows is called a shard. These shards are distributed across multiple server nodes (containers, VMs, bare-metal) in a shared-nothing architecture. This ensures that the shards do not get bottlenecked by the compute, storage and networking resources available at a single node. High availability is achieved by replicating each shard across multiple nodes. However, the application interacts with a SQL table as one logical unit and remains agnostic to the physical placement of the shards.

DocDB supports range and hash sharding natively.