Connection from Lambda to Aurora database fails - amazon-web-services

Question

I've set up an Aurora PostgreSQL compatible database. I can connect to the database via the public address but I'm not able to connect via a Lambda function which is placed in the same VPC.
This is just a test environment and the security settings are weak. In the network settings I tried to use "no VPC" and I tried my default VPC where the database and the lambda are placed. But this doesn't make a difference.
This is my nodejs code to create a simple Select statement:
var params = {
awsSecretStoreArn: '{mySecurityARN}',
dbClusterOrInstanceArn: 'myDB-ARN',
sqlStatements: 'SELECT * FROM userrole',
database: 'test',
schema: 'user'
};
const aurora = new AWS.RDSDataService();
let userrightData = await aurora.executeSql(params).promise();
When I start my test in the AWS GUI I get following errors:
"errorType": "UnknownEndpoint",
"errorMessage": "Inaccessible host: `rds-data.eu-central- 1.amazonaws.com'. This service may not be available in the `eu-central-1' region.",
"trace": [
"UnknownEndpoint: Inaccessible host: `rds-data.eu-central-1.amazonaws.com'. This service may not be available in the `eu-central-1' region.",
I've already checked the tutorial of Amazon but I can't find a point I did't try.

Answer 1

The error message "This service may not be available in the `eu-central-1' region." is absolutely right because in eu-central-1 an Aurora Serverless database is not available.
I configured an Aurora Postgres and not an Aurora Serverless DB.
"AWS.RDSDataService()", what I wanted to use to connect to the RDB, is only available in relation to an Aurora Serverless instance. It's described here: https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/RDSDataService.html.
This is the reason why this error message appeared.