RDS High-availability Edition runs your database in a primary/secondary architecture, with a standby instance ready to take over automatically if the primary fails. It suits more than 80% of production workloads across industries including Internet services, IoT, online retail, logistics, and gaming.
The secondary instance is reserved for failover only — it does not serve read traffic.
Topology
How it works
Data synchronization
The synchronization mode between the primary and secondary instances depends on the parameter template you select.
| Mode | Commit behavior | Degradation |
|---|---|---|
| Semi-synchronous | The transaction commits after the secondary receives the replication log. The secondary does not need to replay the log before the commit is acknowledged. | Automatically degrades to asynchronous mode if the secondary is unavailable or a network interruption occurs between the two instances. |
| Asynchronous | The primary responds to the application immediately and replicates data to the secondary in the background. | No degradation. Workloads on the primary continue normally even if the secondary is unavailable. However, if the primary fails before replication completes, data inconsistencies between the two instances may occur. |
Failover
When the primary instance becomes unavailable, the database system fails over to the secondary instance automatically.
Deployment zones
You can deploy the primary and secondary instances in the same zone or in different zones within the same region. Cross-zone deployment enables cross-zone disaster recovery and improves availability.
When the secondary instance is inaccessible, the primary instance is backed up in real time. Near the end of each backup, a FLUSH TABLE WITH READ LOCK (FTWRL) statement is executed, which holds a global lock for up to 5 seconds and places the primary in read-only mode during that period.
Features
| Feature | Description |
|---|---|
| Auto scaling | Automatically scales resources based on workload demand. |
| Backup and restoration | Backs up your data and restores it when needed. |
| Performance optimization | Provides tools for monitoring and tuning database performance. |
| SQL Explorer | Stores logs of all executed statements for up to five years, enabling full operation traceability for data security and audit requirements. |
Limits
The primary and secondary instances must be in the same region.
The secondary instance is not accessible to external services and cannot serve read traffic.
Create an instance
To create an ApsaraDB RDS for MariaDB instance on RDS High-availability Edition, see Create an ApsaraDB RDS for MariaDB instance.
FAQ
Can I read from the secondary instance directly?
No. The secondary instance is reserved for failover and is not accessible to external services.
Can I downgrade from RDS High-availability Edition to RDS Basic Edition?
No, direct downgrade is not supported. To move to RDS Basic Edition:
Purchase a new RDS Basic Edition instance.
Migrate your data to the new instance. See Migrate data between RDS instances.
Release the original instance.