Help Center/ Document Database Service/ User Guide (Ally Region)/ Introduction/ Basic Concepts/ Cluster
Updated on 2026-01-12 GMT+08:00
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Cluster

Each DDS cluster consists of a config node, and multiple dds mongos and shard nodes. The following diagram shows the node relationships.

Figure 1 Diagram of node relationships

dds mongos

A dds mongos is a router for reading and writing data, providing a unified interface for accessing DB instances.
  • Each DB instance has 2 to 32 dds mongos nodes. You can specify the quantity.
  • A dds mongos reads configuration settings from the config node and allocates read and write requests to shard nodes. You can connect to a dds mongos directly.

config

A config stores configuration settings for DB instances and consists of one replica set.

You cannot connect to a config node directly.

shard

Shards are used to store user data.
  • Each Community Edition instance has 2 to 32 shard nodes. You can specify the quantity.
  • Each shard node is deployed as a replica set to ensure data redundancy and high reliability.
  • You cannot connect to a shard node directly.
Parent topic: Basic Concepts