AWS Lambda inside vs outside a VPC — what actually happens to your traffic

This video breaks down AWS Serverless Network Architecture diagrams, focusing on how Lambda functions interact within a VPC and across different AWS accounts. We explore the critical role of VPC endpoints for private communication with AWS services like S3 and Kinesis, ensuring secure and efficient data flow. Understanding this AWS networking setup is key for robust cross account access and optimal AWS architecture.

Most engineers don't realize: the moment you put Lambda in a VPC, it loses access to every AWS service. S3, SQS, Kinesis, KMS — all gone unless you add VPC endpoints.

This carousel shows the 3 levels:

1️⃣ Lambda outside VPC — can reach AWS services, can't reach RDS
2️⃣ Lambda inside VPC with endpoints — can reach everything privately, no internet needed
3️⃣ Cross-account via Transit Gateway — Lambda in Account A reaches Kinesis in Account B, fully private

The one endpoint everyone forgets: KMS. If your data is encrypted (SSE-KMS), Lambda's SDK calls kms:Decrypt behind the scenes. No KMS endpoint = silent timeout.

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Видео AWS Lambda inside vs outside a VPC — what actually happens to your traffic канала YV Labs by Vidh Yasa