How do I connect to a Postgres RDS with lambda using IAM?

[beckerrobin]

My setup is I have my the IAM access key and secret in a .env file in the root (AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY).
Using the following I get the error

× Error: getaddrinfo ENOTFOUND rds-data.eu-north-1.amazonaws.com
at GetAddrInfoReqWrap.onlookup [as oncomplete] (node:dns:107:26)

Code:

const client = new RDSData({
    region: "eu-north-1",
    credentials: fromNodeProviderChain(),
  });

  const response = await client.executeStatement({
    resourceArn: "arn:aws:rds:<redacted>:db:database-1",
    secretArn: 'arn:aws:secretsmanager:<redacted>:secret:test-<redacted>',
    database: "test",
    sql: "SELECT * FROM t1;"
  });

  client.destroy();

Changing to the following instead returns

× [504] - Lambda timeout.

const client = new RDSData({
    region: "eu-north-1",
    credentials: fromNodeProviderChain(),
    endpointProvider: () => { return { url: "https://database-1.<redacted>.eu-north-1.rds.amazonaws.com" } }
  });

Switing to using the node-postgres package works perfectly. What am I missing?