DB Instance Introduction

Currently, RDS DB instances are classified into the following types:

Different series support different DB engines and instance specifications.

**Table 1** DB instance types
DB Instance Type	Description	Notes	Scenarios
Single	Uses a single-node architecture. More cost-effective than the mainstream primary/standby DB instances.	If a fault occurs on a single instance, the instance cannot recover in a timely manner.	Personal learning Microsites Development and testing environment of small- and medium-sized enterprises
Primary/Standby	Uses an HA architecture. A pair of primary and standby DB instances shares the same IP address and can be deployed in different AZs.	When a primary instance is being created, a standby instance is provisioned synchronously to provide data redundancy. The standby instance is invisible to you after being created. If the primary instance fails, a failover occurs, during which database connection is interrupted. If there is a replication delay between the primary and standby instances, the failover takes an extended period of time. The client needs to be able to reconnect to the instance.	Production databases of large and medium enterprises Applications for the Internet, Internet of Things (IoT), retail e-commerce sales, logistics, gaming, and other industries
Cluster	Uses the Microsoft Always On architecture with one master node, one slave node, and up to five read-only nodes. It features higher availability, reliability, and scalability.	Only for RDS for SQL Server.	Finance industry Internet industry Hotel industry Online education