This topic introduces PPAS read-only instances. If your application initiates a small number of write requests but a large number of read requests, a single instance may not be able to resist the read pressure. As a result, services may be affected. To achieve the elastic expansion of the read ability and share the pressure of the database, you can create one or more read-only instances in a region. The read-only instances can handle massive read requests and increase the application throughput.


A read-only instance is a read-only copy of the master instance. Changes to the master instance are also automatically synchronized to all relevant read-only instances.

  • RDS PPAS 10.0 supports read-only instances while PPAS 9.3 does not.
  • The configuration of the master instance must be at least 8-core 32 GB (dedicated or dedicated-host instance).
  • Each read-only instance adopts a single-node architecture (without slave nodes).
The following figure shows the topology of read-only instances.pgsql拓扑图


The billing method of read-only instances is Pay-As-You-Go. For more information, see Pricing.


Read-only instances offer the following features:

  • Billing method: Pay-As-You-Go. This method is more flexible and cost-effective.
  • Region and zone: Read-only instances are in the same region as the master instance, but can be in a different zone from the master instance.
  • Specifications and storage: Specifications and storage of read-only instances cannot be lower than those of the master instance.
  • Network type: The network type of read-only instances can be different from that of the master instance.
  • Account and database management: Users manage accounts and databases through the master instance rather than read-only instances.
  • Whitelist: When read-only instances are created, they automatically copy the whitelist of the master instance, but the whitelists of read-only instances are independent. You can modify the whitelists of the read-only instances by referring to Configure a whitelist for an RDS PPAS instance.
  • Monitoring and alarms: You can monitor system performance indicators, including the disk capacity, IOPS, number of connections, and CPU usage.


  • Each master instance can have up to five read-only instances.
  • Read-only instances do not support backup settings or manual backups.
  • You cannot migrate data to read-only instances.
  • You cannot create or delete databases for read-only instances.
  • You cannot create or delete accounts for read-only instances.
  • You cannot authorize accounts or modify account passwords for read-only instances.


Does an account created in the master instance have permissions on read-only instances?

The accounts created in the master instance are automatically synchronized to read-only instances. However, you cannot manage the accounts in the read-only instances. The accounts only have the read permissions for the read-only instances.