Advantages

DDS provides several types of DB instances with high reliability and scalability. You can manage them using various O&M tools in a visual way.

There are many instance types to meet your requirements in different scenarios.

**Table 1** Architecture
Instance Architecture	Description	Application Scenario
Cluster	A DDS cluster consists of three types of nodes: mongos, shard, and config. You can select the number of mongos and shard nodes and the cluster configuration you need based on your performance requirements.	Cluster instances are recommended for service systems that require both high availability and scalability.
Replica set	A DDS replica set consists of three nodes: primary, secondary, and hidden. Data is automatically synchronized between nodes to ensure high data reliability. If a primary node goes down or becomes faulty, the replica set elects a secondary node as a new primary node and continues normal operations.	Replica set instance suits small- and medium-sized service systems that require high availability.
Single node	While not as robust as replica sets, single node architecture can be a less expensive way to visualize O&M and provide elastic scaling.	Single node instances are useful for R&D, testing, and non-core data storage of enterprises.

DDS allows you to change the storage space, node quantity, CPU, and memory of an instance.

A web-based console provides comprehensive monitoring information, making your operations easy and visual.

VPCs, subnets, security groups, storage encryption, SSL, and DDoS protection are provided to defend against various malicious attacks and ensure data security.
DDS supports audit logs that record your operations on databases or collections, helping you audit database security and analyze root cause of faults.
Fine-grained permission management is supported.

Backup and restoration
DDS supports full backup, incremental backup, and point-in-time backup and restoration of replica sets. Backup data can be stored for up to 732 days.
Monitoring and alarm reporting
DDS monitors instance metrics. You can customize the objects you want to monitor and configure notification policies to learn about the database service status in a timely manner.

DDS also boasts outstanding service availability, data durability, system security, and maintenance cost. For details, see Comparison Between DDS and On-Premises Databases.