Networking

• Lambda supports 2 networking modes Public which is default & VPC based
• A lambda running in public mode it has access to AWS public services as well as internet
• Lambda running in public mode has best performance
• Lambda in public mode but will not have access to vpc based services
• Lambda running in a vpc can not access anything outside vpc without networking changes
• Lambdas need one ENI per subnet and security group combination in a VPC.
• The ENIs are created when a lambda function is created. It take about 90s but is done once.