aws-rds: defaultDatabaseName name constrain change caused database replacement.

[sasuolanderSito]

Describe the bug

When updating DatabaseCluster with defaultDatabaseName value ${envName}-db caused error "DatabaseName must begin with a letter and contain only alphanumeric characters".
We where forced change code into " defaultDatabaseName: ${envName}_db," and doing some data recovery hurdles.

I think CDK has been doing defaultDatabaseName value sanitatiotion and now this functionality is removed.

Regression Issue

• Select this option if this issue appears to be a regression.

Last Known Working CDK Library Version

2.234.1

Expected Behavior

Name with "-" should be allowed.

Current Behavior

Cannot use "-" symbol in database name.

Reproduction Steps

Create aurora db on version 2.234.1 with defaultDatabaseName containning "-" in name.
CDK allow database creation.
Updated newer CDK version.
Try to update stack and get errro "DatabaseName must begin with a letter and contain only alphanumeric characters.

Possible Solution

No response

Additional Information/Context

No response

AWS CDK Library version (aws-cdk-lib)

2.234.1

AWS CDK CLI version

--

Node.js Version

24

OS

Windows

Language

TypeScript

Language Version

No response

Other information

No response

[pahud]

Hi @sasuolanderSito,

┌────────────────────────────────────────────────────────────┐
│ 🔴 Reported State                                          │
│ Hyphenated defaultDatabaseName rejected on stack update    │
│ after upgrading CDK past 2.234.1                           │
└─────────────────────────────┬──────────────────────────────┘
                              │
                              ▼
┌────────────────────────────────────────────────────────────┐
│ 🔍 Root Cause                                              │
│ Not confirmed — error originates from the RDS API, not     │
│ CDK; CDK passes the name through verbatim (cluster.ts)     │
└─────────────────────────────┬──────────────────────────────┘
                              │
                              ▼
┌────────────────────────────────────────────────────────────┐
│ 🟢 Suggested Fix                                           │
│ Need cdk diff + stack events + exact versions to pin down  │
│ what triggered the failing update                          │
└────────────────────────────────────────────────────────────┘

Thanks for the report. I wasn't able to reproduce this with the steps provided. I synthesized a cluster with defaultDatabaseName: 'stage-db' on both 2.234.1 and the latest 2.266.0 — both succeed, and the rendered AWS::RDS::DBCluster resource is byte-identical between the two versions. From my view this rules out the sanitization theory: CDK has never validated or sanitized defaultDatabaseName; it's passed through verbatim in both versions, and that error string doesn't exist anywhere in aws-cdk-lib:

aws-cdk/packages/aws-cdk-lib/aws-rds/lib/cluster.ts

Line 960 in 068c9f9

databaseName: props.defaultDatabaseName,

aws-cdk/packages/aws-cdk-lib/aws-rds/lib/cluster.ts

Line 987 in e8d9160

databaseName: props.defaultDatabaseName,

That message is an RDS API error, and RDS only validates DatabaseName when creating a cluster (it's a create-only property in CloudFormation). Since a CDK upgrade alone produces no change to the cluster resource, we're missing whatever actually triggered the failing update in your stack.

Could you share:

• The CDK version you upgraded to (the issue only lists 2.234.1 as last working)
• Your engine and version (aurora-mysql / aurora-postgresql)
• cdk diff output between the two CDK versions on this stack
• The CloudFormation stack events from the failed update (which resource/property was changing)

With those we can determine whether CDK changed something replacement-triggering on your cluster (a real bug we'd want to fix) or whether this is RDS service-side validation behavior.

[sasuolanderSito]

1. The CDK version
   aws-cdk-lib: ^2.234.1
   aws-cdk (CLI): 2.1101.0

2. Your engine and version
   Engine: aurora-postgresql

Version: 17.4
(Defined in code as: AuroraPostgresEngineVersion.of('17.4', '17'))

3. cdk diff output between the two CDK versions on this stack
   Plaintext
   Stack dev-sasutest
   Security Group Changes
   ┌───┬──────────────────────────────┬─────┬────────────┬─────────────────┐
   │ │ Group │ Dir │ Protocol │ Peer │
   ├───┼──────────────────────────────┼─────┼────────────┼─────────────────┤
   │ + │ ${drn-db-sg-db-sasu.GroupId} │ In │ TCP 5432 │ 10.208.140.0/22 │
   │ + │ ${drn-db-sg-db-sasu.GroupId} │ Out │ Everything │ Everyone (IPv4) │
   └───┴──────────────────────────────┴─────┴────────────┴─────────────────┘

Parameters
[+] Parameter BootstrapVersion BootstrapVersion: {"Type":"AWS::SSM::Parameter::Value","Default":"/cdk-bootstrap/hnb659fds/version","Description":"Version of the CDK Bootstrap resources in this environment, automatically retrieved from SSM Parameter Store. [cdk:skip]"}

Resources
[+] AWS::EC2::SecurityGroup drn-db-sg-db-sasu drndbsgdbsasuB18FA5E7
[+] AWS::SecretsManager::Secret db-sasu dbsasu9EB72D76
[+] AWS::SecretsManager::SecretTargetAttachment db-sasu/Attachment dbsasuAttachment0E72EDA8
[+] AWS::RDS::DBSubnetGroup AuroraDB/Subnets AuroraDBSubnetsD33687F7
[+] AWS::RDS::DBCluster AuroraDB AuroraDBD2536A33
[+] AWS::RDS::DBInstance AuroraDB/WriterInstance AuroraDBWriterInstanceFA7031FA
4. The CloudFormation stack events from the failed update
The deployment failed during the creation of the AWS::RDS::DBCluster (AuroraDB).

The specific failure reason:

Resource handler returned message: "DatabaseName must begin with a letter and contain only alphanumeric characters. (Service: Rds, Status Code: 400, Request ID: 8e996f61-2f65-468e-8d54-4fb63aae1a4d) (SDK Attempt Count: 1)" (RequestToken: a26317dd-6b7f-5cfd-8d2b-66270eb70890, HandlerErrorCode: InvalidRequest)

Relevant Stack Events:

Plaintext
dev-sasutest | 4/8 | 13.15.12 | CREATE_IN_PROGRESS | AWS::RDS::DBCluster | AuroraDB (AuroraDBD2536A33)
dev-sasutest | 4/8 | 13.15.13 | CREATE_IN_PROGRESS | AWS::RDS::DBCluster | AuroraDB (AuroraDBD2536A33) Resource creation Initiated
dev-sasutest | 4/8 | 13.15.16 | CREATE_FAILED | AWS::RDS::DBCluster | AuroraDB (AuroraDBD2536A33) Resource handler returned message: "DatabaseName must begin with a letter and contain only alphanumeric characters..."
dev-sasutest | 4/8 | 13.15.16 | ROLLBACK_IN_PROGRESS | AWS::CloudFormation::Stack | dev-sasutest The following resource(s) failed to create: [AuroraDBD2536A33]. Rollback requested by user.

[sasuolanderSito]

I rolled back into older version and i got same result. Little bit strange.