ApsaraDB RDS for PostgreSQL enforces quotas and limits across storage, connections, naming, security, and other operational areas. Review the constraints that apply to your configuration before creating an instance.
Specifications and performance
| Item | Limit | Notes |
|---|---|---|
| Storage capacity | Premium Local SSDs: up to 6,000 GB<br>Standard SSDs: up to 6,000 GB<br>ESSDs: up to 64,000 GB<br>Premium ESSDs: up to 64,000 GB | For Premium Local SSDs, the actual limit varies by instance type. This restriction does not apply to standard SSDs or ESSDs. See Primary ApsaraDB RDS instance types. |
| Connections | Up to 76,800 | The exact limit varies by instance type. See Primary ApsaraDB RDS instance types. |
| IOPS | Premium Local SSDs: up to 50,000<br>Cloud disks: see IOPS | — |
| Memory | Premium Local SSDs: up to 512 GB<br>Cloud disks: up to 768 GB | For cloud disk instances, available memory is less than the instance type's total capacity. The underlying OS reserves 500 MB–700 MB, and RDS management services reserve approximately 500 MB. |
Quotas
| Item | Quota | Notes |
|---|---|---|
| Read-only instances | Requires PostgreSQL 10 or later. Read-only instances must reside in the same region as the primary RDS instance.<br><br>Premium Local SSDs:<br>- Up to 5 read-only instances<br>- Primary instance must be a dedicated instance with at least 8 cores and 32 GB of memory<br><br>Standard SSDs or ESSDs:<br>- Up to 32 read-only instances<br>- Each read-only instance uses a single-node architecture with no standby secondary instances | See Overview of read-only ApsaraDB RDS for PostgreSQL instances. |
| Tags | Up to 20 tags per instance. Tag keys must be unique. Up to 50 instances can be tagged in a single operation. | See Add tags to ApsaraDB RDS instances. |
| Free backup storage quota | Premium Local SSDs: 50% × purchased storage capacity<br>Standard SSDs or ESSDs: 200% × purchased storage capacity<br><br>Excess backup storage (GB, rounded up) = data backup size + log backup size − free quota | Cloud disk instances support snapshot backups only. Premium Local SSD instances support physical backups only. See Back up an ApsaraDB RDS for PostgreSQL instance. |
| Backup retention period | Default: 7 days. Maximum: 730 days. | — |
| Error log retention period | 30 days | See View logs. |
| Slow query log retention period | 30 days | See View logs. |
Naming limits
Instance name
2 to 256 characters
Allowed characters: letters, digits, underscores (
_), and hyphens (-)Must start with a letter
Username
2 to 63 characters
Allowed characters: lowercase letters, digits, and underscores (
_)Must start with a letter and end with a letter or digit
Cannot duplicate an existing account username
Cannot start with
pgCannot contain SQL keywords — see SQL Keywords
Database name
Up to 63 characters
Allowed characters: lowercase letters, digits, underscores (
_), and hyphens (-)Must start with a lowercase letter and end with a lowercase letter or digit
Must be unique within the instance
Cannot contain SQL keywords — see SQL Keywords
Security limits
| Item | Limit | Notes |
|---|---|---|
| Password | 8 to 32 characters. Must include at least three of the following character types: uppercase letters, lowercase letters, digits, special characters (! @ # $ % ^ & * () _ + - =). | — |
| Port | Default: 5432. Can be changed based on your business requirements. | — |
| Instance parameters | Most parameters are configurable via the ApsaraDB RDS console or ApsaraDB RDS API. A subset of parameters is locked for stability and security. | See Modify the parameters of an ApsaraDB RDS for PostgreSQL instance. |
| Cloud disk encryption | Can only be enabled when you purchase the instance. Cannot be disabled after enablement. | See Configure the cloud disk encryption feature. |
| Security groups | Up to 10 security groups per instance. Security groups must match the network type of the instance — virtual private cloud (VPC) or classic network. All Elastic Compute Service (ECS) instances in configured security groups can communicate with the RDS instance. | See Configure a security group. |
| IP address whitelists | Up to 50 IP address whitelists per instance. | See Configure an IP whitelist. |
| Superuser (root) accounts | Not supported. ApsaraDB RDS for PostgreSQL does not provide superuser accounts. | — |
| Privileged accounts | Multiple privileged accounts can be created per instance via the ApsaraDB RDS console or ApsaraDB RDS API. Privileged accounts can disconnect all standard accounts on the instance. | See Create an account. |
| Standard accounts | Created and managed via the ApsaraDB RDS console, ApsaraDB RDS API, or SQL statements. Each standard account requires explicit per-database permission grants. Standard accounts cannot create, manage, or disconnect other accounts. | See Create an account. |
SQL statement limits
SQL statement limits follow open source PostgreSQL. For the full list of supported statements, see SQL Commands. For system-level limits such as maximum identifier length or column count, see PostgreSQL Limits.
Other limits
| Item | Limit | Notes |
|---|---|---|
| Public endpoint | Not assigned by default. Must be manually applied for. | See View and change the endpoints and port numbers. |
| Replication | Primary/secondary replication is supported in all editions except RDS Basic Edition. Secondary RDS instances are invisible to you and cannot be accessed by your applications. | — |
| Instance restart | Restarts must be performed through the ApsaraDB RDS console or ApsaraDB RDS API. | — |
| Tablespace creation | Not supported. | — |