I tried out the Amazon RDS storage change that can now be done up to 4 times in 24 hours

Amazon RDS now allows up to 4 storage modifications per 24 hours, including size changes, type changes, and performance changes. The previous 6-hour cooldown restriction has been removed. We actually performed consecutive storage size changes on RDS for PostgreSQL and confirmed 4 successful modifications and an error on the 5th attempt.

suzuki.ryo

2026.07.16

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Introduction

As of the July 15, 2026 update, Amazon RDS now allows storage size changes, type changes, and performance (IOPS/throughput) changes up to 4 times per 24 hours. The 6-hour cooldown period that was previously required after each storage modification has been removed.

Item	Old Specification	New Specification (From 2026-07-15)
Cooldown after storage modification	6-hour wait required	Next modification possible as soon as optimization completes
Maximum number of modifications per 24 hours	Effectively 4 (but with a 6-hour wait required after each modification)	4 (can be executed consecutively as soon as optimization completes)
Modifications during storage-optimization	Not allowed	Not allowed (no change)

A similar relaxation was applied on the Amazon EBS side in January 2026 as a precursor. This time, the same restriction relaxation that had been applied to EBS was also introduced for RDS storage modifications. The EBS-side verification is summarized in the following article.

This article verifies consecutive storage size changes on RDS for PostgreSQL, confirming that 4 changes succeed and that the 5th attempt results in an error. Storage type changes and IOPS changes have already been verified in the EBS (EC2) article, so they are out of scope for this article.

Verification Details

Verification Environment

Item	Value
AWS CLI	2.35.22
Region	ap-northeast-1
Instance Identifier	test-storage-4mod
Engine	PostgreSQL 18.3
Instance Class	db.t4g.micro
Storage Type	gp3
Initial Storage	20 GB
Initial IOPS	3000
Initial Throughput	125 MB/s
Multi-AZ	None (Single-AZ)
Public Access	None
Deletion Protection	None
Automated Backup Retention Period	1 day

Creating the RDS Instance

The following command was used to create the RDS for PostgreSQL instance for verification.

aws rds create-db-instance \
    --db-instance-identifier test-storage-4mod \
    --db-instance-class db.t4g.micro \
    --engine postgres \
    --engine-version 18.3 \
    --allocated-storage 20 \
    --storage-type gp3 \
    --iops 3000 \
    --storage-throughput 125 \
    --master-username postgres \
    --manage-master-user-password \
    --no-multi-az \
    --no-publicly-accessible \
    --no-deletion-protection \
    --backup-retention-period 1 \
    --region ap-northeast-1

It became available in approximately 6 minutes.

aws rds wait db-instance-available --db-instance-identifier test-storage-4mod --region ap-northeast-1

Checking gp3 Storage Size Constraints

Before performing consecutive modifications, use describe-valid-db-instance-modifications to check the modifiable storage sizes.

aws rds describe-valid-db-instance-modifications \
    --db-instance-identifier test-storage-4mod \
    --region ap-northeast-1

The StorageSize included in ValidStorageOptions in the response was as follows.

"StorageSize": [
    {
        "From": 22,
        "To": 65536,
        "Step": 1
    }
]

For the initial size of 20 GB, the minimum value that could be specified for the next modification was 22 GB. There is a constraint for gp3 storage size changes that requires "increasing by at least 10% from the current size." The original plan was to change in 1 GB increments, but this constraint made that impossible. Summarizing the valid minimum sizes confirmed via describe-valid-db-instance-modifications at each step:

Current Size	Next Valid Minimum Size	Increment
20 GB	22 GB	+2 GB (10%)
22 GB	25 GB	+3 GB (≈14%)
25 GB	28 GB	+3 GB (12%)
28 GB	31 GB	+3 GB (≈11%)
31 GB	35 GB	+4 GB (≈13%)

1st Modification: 20 GB → 22 GB

aws rds modify-db-instance \
    --db-instance-identifier test-storage-4mod \
    --allocated-storage 22 \
    --apply-immediately \
    --region ap-northeast-1

The PendingModifiedValues.AllocatedStorage in the response was 22. The status was checked using the following command.

aws rds describe-db-instances \
    --db-instance-identifier test-storage-4mod \
    --query 'DBInstances[0].DBInstanceStatus' \
    --output text \
    --region ap-northeast-1

Status transition: available → modifying → storage-optimization → available
Time required for storage-optimization: approximately 10 minutes

2nd Modification: 22 GB → 25 GB

aws rds modify-db-instance \
    --db-instance-identifier test-storage-4mod \
    --allocated-storage 25 \
    --apply-immediately \
    --region ap-northeast-1

The PendingModifiedValues.AllocatedStorage in the response was 25. The status was checked in the same way as the 1st modification.

Status transition: available → modifying → storage-optimization → available
Time required for storage-optimization: approximately 15 minutes

3rd Modification: 25 GB → 28 GB

aws rds modify-db-instance \
    --db-instance-identifier test-storage-4mod \
    --allocated-storage 28 \
    --apply-immediately \
    --region ap-northeast-1

The PendingModifiedValues.AllocatedStorage in the response was 28. The status was checked in the same way.

Status transition: available → modifying → storage-optimization → available
Time required for storage-optimization: approximately 20 minutes

4th Modification: 28 GB → 31 GB

aws rds modify-db-instance \
    --db-instance-identifier test-storage-4mod \
    --allocated-storage 31 \
    --apply-immediately \
    --region ap-northeast-1

The PendingModifiedValues.AllocatedStorage in the response was 31. The status was checked in the same way.

Status transition: available → modifying → storage-optimization → available
Time required for storage-optimization: approximately 20 minutes

5th Modification: 31 GB → 35 GB (Exceeding the 24-hour limit)

After the 4th optimization completed and the instance returned to available, the 5th modification was attempted.

aws rds modify-db-instance \
    --db-instance-identifier test-storage-4mod \
    --allocated-storage 35 \
    --apply-immediately \
    --region ap-northeast-1

An InvalidParameterCombination error occurred.

An error occurred (InvalidParameterCombination) when calling the ModifyDBInstance operation: You can't modify the storage because you've exceeded the maximum number of storage modifications allowed in the last 24 hours. Try again in approximately 22 hours.

Note: Attempting Modifications During storage-optimization

Attempting the next modification while storage-optimization is in progress also results in an InvalidParameterCombination error.

An error occurred (InvalidParameterCombination) when calling the ModifyDBInstance operation: You can't currently modify the storage of this DB instance because the previous storage change is being optimized.

Cleanup

After verification, the instance was deleted. Since this was for verification purposes, it was deleted without retaining the final snapshot or automated backups.

aws rds delete-db-instance \
    --db-instance-identifier test-storage-4mod \
    --skip-final-snapshot \
    --delete-automated-backups \
    --region ap-northeast-1

Summary

We were able to confirm that the "maximum 4 storage modifications per 24 hours" relaxation that had been applied to EBS first has now also been applied to RDS. Feel free to take advantage of this for gradual capacity increases in production environments or when searching for the optimal storage size in load testing environments.