Access RDS from VPC Lambda

Question

Is it possible to access a publicly available RDS instance from a Lambda expression in the same VPC, without using a NAT? Could you please point me in the right direction to confugure this? Thanks.

RDS and Lambda have the same VPC, the same Subnets, the same Security group. The security group has 2 inbound rules:

1. All Type - All Protocol - All Port Range - Source ALB security group
2. All Type - All Protocol - All Port Range - Source security group itself

Is that correct?

Answer 1

The recommended configuration is:

• Create a Security Group for the AWS Lambda function (Lambda-SG). It does not require any inbound rules.
• Create a Security Group for the Amazon RDS db instance (DB-SG). It should allow an Inbound connection on the appropriate port (3306?) from Lambda-SG.

That is, DB-SG should specifically reference Lambda-SG as the source of the inbound connection.