Let's go on a journey through the world of multi-tenant architectures on AWS using serverless technologies. In this talk, we will uncover the key aspects of multi-tenancy, including security, tenant isolation, and performance. We will learn how to utilise Cognito for authentication, DynamoDB to store millions of tenant-partitioned records and lambda for compute. We will also explore different deployment models and their tradeoffs, and, finally, we will learn how to implement policy-based isolation with IAM to keep our execution context tied to one specific tenant and avoid data leakage. By the end of this talk, you will feel more confident building SaaS applications on AWS with serverless technologies and you will have learned some of the many insights that come from the AWS Well-Architected SaaS Lens.