Redshift serverless client api call list_workgroups gets timedout in lambda function

Question

I have a lambda function which uses below code to list redshift serverless workgroups.

client = boto3.client("redshift-serverless")
res = client.list_workgroups()

I have configured local subnets for lambda which does not have internet access. I have my vpc endpoints configured for local subnets.

My redshift provisioned cluster api describe_clusters() works fine. Does anyone know why I'm facing issue only for redshift serverless api calls.

Thanks

I tried to add full access to my redshift serverless and lambda security groups which did not work.