I actually measured the 16 ACU scaling of Aurora Serverless v2
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Introduction
On September 30, 2026, it was announced that Aurora Serverless v2 had been enhanced to increase capacity by up to 16 ACU at the start of scaling.
In August 2026, a feature was enhanced to increase capacity by up to 12 ACU all at once immediately after scaling begins, and this update expands that further.
This article, similar to the previous one, presents the results of attempting to expand the minimum capacity from 1 to 30.
Test Environment
| Item | Value |
|---|---|
| Engine | Aurora PostgreSQL 16.15 (Serverless v2) |
| Region | us-east-1 |
| PlatformVersion | 4 |
Measurement Method
The MinCapacity was raised from 1 to 30.
aws rds modify-db-cluster \
--db-cluster-identifier <cluster ID> \
--serverless-v2-scaling-configuration MinCapacity=30,MaxCapacity=30 \
--apply-immediately
After the change, the CloudWatch metric ServerlessDatabaseCapacity was retrieved at period=1 (1-second intervals) to observe the capacity transition.
aws cloudwatch get-metric-statistics \
--namespace AWS/RDS \
--metric-name ServerlessDatabaseCapacity \
--dimensions Name=DBInstanceIdentifier,Value=<instance ID> \
--start-time <start time> \
--end-time <end time> \
--period 1 \
--statistics Maximum
This procedure was performed twice. For each run, it was confirmed that after the previous measurement reached 30 ACU, the MinCapacity was returned to 1 and dropped to 1.0 ACU before starting.
Measurement Results
The results of the first measurement are as follows.
| Elapsed time since MinCapacity change | ACU |
|---|---|
| +0 seconds | 1.0 |
| +17 seconds | 1.0 |
| +18 seconds | 17.0 |
| +18 to +178 seconds | 17.0 → 30.0 (increasing by 0.5 ACU approximately every 6 seconds) |
| +178 seconds | 30.0 |
+17 seconds and +18 seconds are consecutive data points, with 16 ACU increasing during this 1-second interval. The "up to 16 ACU within 1 second" stated in the announcement is considered to correspond to this sudden increase.
The second measurement produced the same results.
Comparison with August Measurement
| Item | August 2026 (12 ACU enhancement) | This time (16 ACU enhancement) |
|---|---|---|
| Capacity increase (measured) | +12.5 ACU (1.0 → 13.5) | +16 ACU (1.0 → 17.0) |
| Time to reach 30 ACU | 225 seconds | 178 seconds |
The time to reach 30 ACU was reduced by 47 seconds.
Summary
As announced, it was confirmed that the capacity increase from 1 ACU has become 16 ACU, and the time to reach 30 ACU was reduced by 47 seconds compared to the August measurement. Improved automatic tracking of spikes and faster tracking speed in configurations with a higher MinCapacity setting can also be expected.
Clusters on older PlatformVersions should be upgraded to the latest version to verify capacity tracking speed. Faster tracking may allow for a gradual reduction of the MinCapacity that was set higher in anticipation of insufficient DB performance, and if achieved, this could lead to cost savings.
