Measuring the Initial Capacity Performance of the Aurora Serverless v2 Update "Up to 12 ACUs Within 1 Second"
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Introduction
On August 5, 2026, an improvement to the initial capacity when scaling up in Aurora Serverless v2 was announced.
In this article, I triggered a scale-up by changing MinCapacity and measured the progression from 1 ACU to 30 ACU at one-second granularity using CloudWatch metrics.
Test Details
Test Environment
| Item | Value |
|---|---|
| Engine | Aurora PostgreSQL Serverless v2 |
| Region | ap-northeast-1 (Tokyo) |
| PlatformVersion | 4 |
| Capacity settings before change | MinCapacity=1, MaxCapacity=30 |
| Capacity settings after change | MinCapacity=30, MaxCapacity=30 |
| Load | None (MinCapacity change only) |
The PlatformVersion was confirmed with ServerlessV2PlatformVersion in describe-db-clusters.
Measuring Scale-Up Speed
I raised MinCapacity from 1 to 30 and measured how the capacity followed.
aws rds modify-db-cluster \
--db-cluster-identifier my-cluster \
--serverless-v2-scaling-configuration MinCapacity=30,MaxCapacity=30 \
--apply-immediately
I retrieved the progression of the ServerlessDatabaseCapacity metric with period=1.
aws cloudwatch get-metric-statistics \
--namespace AWS/RDS \
--metric-name ServerlessDatabaseCapacity \
--dimensions Name=DBInstanceIdentifier,Value=my-instance \
--start-time 2026-08-06T03:29:00Z \
--end-time 2026-08-06T03:35:00Z \
--period 1 \
--statistics Maximum
The criteria are as follows.
- Change time: The time
modify-db-clusterwas executed - Start time: The first data point where ACU exceeded 1.0
- Completion time: The first data point where ACU reached 30.0
Measurement Results
| Event | Elapsed time from change | ACU |
|---|---|---|
| MinCapacity change | 0 seconds | 1.0 |
| Scale-up start | 15 seconds | 1.0 |
| Initial expansion complete | 16 seconds | 13.5 |
| Reached 30 ACU | About 3 min 45 sec | 30.0 |
Scale-up started 15 seconds after the change, and an expansion of +12.5 ACU, from 1.0 ACU to 13.5 ACU, completed in one second. After 13.5 ACU, it increased gradually, and it reached 30 ACU about 3 minutes 45 seconds after the change.
Only the change points in the ACU progression are excerpted (intervals where the same value continues are omitted).
| Elapsed time | ACU |
|---|---|
| 0 seconds | 1.0 |
| 16 seconds | 13.5 |
| 26 seconds | 14.0 |
| 33 seconds | 15.0 |
| 1 min 00 sec | 16.5 |
| 1 min 30 sec | 18.5 |
| 2 min 00 sec | 21.0 |
| 2 min 30 sec | 23.5 |
| 3 min 00 sec | 26.0 |
| 3 min 45 sec | 30.0 |
This measurement is a single measurement by changing the MinCapacity setting. Autoscaling triggered by workload load may behave differently.
Summary
With this update, it is now possible to expand by up to 12 ACU within one second. In this simple measurement as well, the expansion from 1 to 13.5 ACU took one second, and reaching 30 ACU completed in about 3 minutes 45 seconds.
The latest platform (4) has been announced to offer up to 30% performance improvement and double the autoscaling speed.
Together with this update, it may be possible to keep MinCapacity lower than before. If you have set a high MinCapacity on an older platform and the cost of Aurora Serverless is an issue, we recommend updating to the latest platform (4) and reviewing your ACU settings.
