RDS-PostgreSQL supports read-only instances.
In scenarios with little write requests but a large amount of write requests, a single instance may be unable to handle the read pressure, and service performance may be affected. To expand the read ability and offload pressure on the database, you can create one or more read-only instances in a region. These read-only instances can meet a large number of read requests and increase application throughput. You need to separately configure connection addresses for the primary instance and each read-only instance on your applications so that all write requests can be sent to the primary instance and read requests to the read-only instances.
A read-only instance uses the architecture of a single physical node (without a slave node or backup node). The native streaming replication function of PostgreSQL is used to synchronize changes from the primary instance to all read-only instances. The data synchronization between the primary instance and the read-only instance is not affected by network latency.
Features
• The specification of a read-only instance can be different from that of a primary instance. However, its specification must be greater than or equal to 1/2 of that of the primary instance. For instance, if the primary instance specification is 8C16G, the read-only instance specification is at least 4C8G. Specification expansion to facilitate elastic upgrading.
• All read-only instances are synchronized through the primary instance. You do not need to maintain accounts and databases.
• System performance monitoring is supported. RDS-PostgreSQL provides a monitoring view of nearly 20 system performances, such as disk capacity, IOPS, number of connections, CPU usage, network traffic, etc. You can easily view the load of read-only instances.
Service Requirements
• Limit of numbers: Up to five read-only instances can be created for a primary instance.
• Life cycle: The RDS-PostgreSQL read-only instances can be unsubscribed separately. However, if the primary instance is unsubscribed, the corresponding read-only instances are also unsubscribed.
• Billing mode: Only the Payment by Volume billing mode is supported.
• Backup settings: Backup settings or temporary backups are not supported.
• Instance restoration: Creating a temporary instance by backing up files or at any point in time is not supported, and overwriting an instance by a backup set is not supported.
• Data migration: Migrating data to a read-only instance is not supported.
• Database Management: Database creation or deletion is not supported. The database for a read-only instance is the same as that for the primary instance.
• Account management: Read-only instances do not provide permission to create an account. To add a read-only instance account, please operate this on a primary instance.