Configure the DB instance to allow public access Update the DB instance security group to allow access from the Lambda public address space for the AWS Region

Deploy the Lambda functions inside the VPC Attach a network ACL to the Lambda subnet Provide outbound rule access to the VPC CIDR range only Update the DB instance security group to allow traffic from 0 0 0 0/0

Deploy the Lambda functions inside the VPC Attach a security group to the Lambda functions Provide outbound rule access to the VPC CIDR range only Update the DB instance security group to allow traffic from the Lambda security group

Peer the Lambda default VPC with the VPC that hosts the DB instance to allow direct network access without the need for security groups