Configuring Auto Throttling

Scenarios

Auto throttling automatically controls traffic by presetting criteria such as a CPU usage threshold and the maximum number of active connections. When these criteria are met, the system automatically throttles sessions to ensure core workload availability during sudden traffic surges or read/write exceptions.

Supported Versions

• All versions of RDS for PostgreSQL 15 and above
• RDS for PostgreSQL 14: 14.8 and later
• RDS for PostgreSQL 13: 13.11 and later
• RDS for PostgreSQL 12: 12.15 and later
• RDS for PostgreSQL 11: 11.20 and later

Constraints

• Auto throttling terminates only SELECT sessions.
• Throttling is triggered when the throttling policy criteria are met within the specified time window.
• A session is terminated if it falls within the throttling range and exceeds the maximum number of active connections when throttling is triggered.
• Sessions are terminated in batches, with a maximum of 10 sessions terminated per batch. Sessions that have been running for the longest duration are terminated first.
• The auto throttling history is stored on the primary node. It may be cleared after tasks such as primary/standby failovers, instance class changes, or minor version upgrades are performed.
• Within the throttling time window, after a throttling event finishes, subsequent throttling will be triggered only when the throttling policy criteria (CPU usage, active session count, and duration) are met again.

Procedure

1. Log in to the RDS console.
2. Click in the upper left corner and select a region.
3. On the Instances page, click the target instance to go to the Summary page.
4. In the navigation pane, choose SQL Analysis and Tuning under DBA Assistant.
5. Click the Auto Throttling tab.
   

   Auto Throttling is a paid value-added feature of the Advanced DBA Assistant. You need to upgrade DBA Assistant first.

6. In the displayed dialog box, check the details and pricing of the value-added feature and click Upgrade.
   Figure 1 Subscribing Advanced DBA Assistant
   

7. After the subscription, click Auto Throttling and set the throttling range, time, and policy. When the criteria are met, the system automatically throttles sessions to ensure core workload availability.
   Figure 2 Auto Throttling
   

   Table 1 Parameters

   Parameter	Description
   Database	Name of the database for which auto throttling needs to be enabled. If left blank, auto throttling will be applied to all databases by default.
   Username	Username to which auto throttling is applied.
   Time Window	Time period during which auto throttling can be triggered.
   Max. Duration (min)	Maximum duration for each auto throttling event. For example, you set Max. Duration (min) to 1, Active sessions to 2000, and Max. Active Connections to 1000. When these criteria are met within the time window, throttling triggers. If active connections drop below 1,000 after 10 seconds, throttling ends early. If active connections fail to drop below 1,000 after 1 minute, throttling also ends.
   vCPU usage (%)	vCPU usage threshold for the instance (≥ 70%).
   Active sessions	Threshold for active sessions. Value range: 1 to 5000
   Evaluation operator	Evaluation logic for vCPU usage and active sessions. Throttling can be triggered based on vCPU usage or active sessions alone, or both using an "AND" or "OR" operator.
   Duration (min)	How long vCPU usage and active sessions have exceeded the specified values. You can set the duration to 5, 15, or 30 minutes. For example, if you set vCPU usage (%) to 90%, Active sessions to 1000, and Duration (min) to 30, auto throttling will be triggered only when both vCPU usage and active sessions exceed those thresholds continuously for 30 minutes.
   Max. Active Connections	Connection threshold to stop auto throttling once active connections fall below this value. The value ranges from 1 to 5000.

8. Click OK.

   Verify that an auto throttling record is generated on the page every time auto throttling is triggered. You can also view historical auto throttling records.