Introducing Read Replicas

Introduction

RDS for MariaDB supports read replicas.

In read-intensive scenarios, a single DB instance may be unable to handle the read pressure and service performance may be affected. To offload read pressure on the primary DB instance, you can create one or more read replicas in the same region as the primary instance. These read replicas can process a large number of read requests and increase application throughput.

A read replica uses a single-node architecture (without a standby node). Changes to the primary DB instance are also automatically synchronized to all associated read replicas through the native MariaDB replication function. The synchronization is not affected by network latency. Read replicas and the primary DB instance must be in the same region but can be in different AZs.

Applicable Scenario

In read-intensive scenarios, read replicas help offload read pressure from the primary instance.

Data is replicated from the primary instance to read replicas asynchronously. Although there is a replication delay, the data on read replicas will eventually be consistent with that on the primary instance. You can use read replicas if you do not mind such a replication delay.

Billing Standards

Read replicas are billed on a pay-per-use basis.

Functions

Read replica specifications can be different from primary DB instance specifications. It is recommended that the read replica specifications be greater than or equal to the primary DB instance specifications to prevent long delay and high load.
Pay-per-use billing is supported. You only pay for what you use.
Read replicas support system performance monitoring.
RDS provides up to 20 monitoring metrics, including storage space, IOPS, database connections, CPU usage, and network traffic. You can view these metrics to learn about the load on read replicas.

Constraints

Up to five read replicas can be created for a DB instance. To create up to 10 read replicas for a DB instance, contact customer service to apply for the required permissions.
You can purchase read replicas only for your created DB instance.
All databases and tables in the primary instance are synchronized to read replicas. Data of the primary instance, standby instance, and read replicas is consistent.
Read replicas do not support automated backups or manual backups.
Read replicas do not support restoration from backups to new, existing, or original read replicas.
Data cannot be migrated to read replicas.
Read replicas do not support database creation and deletion.
Read replicas do not support database account creation. Create database accounts on the primary DB instance. For details, see Creating a Database Account.
Read replicas cannot be recycled after they are deleted.