This summary provides an overview of building a serverless multi-tenant SaaS application with AWS and Fauna. It explains the challenges of balancing isolation with operational efficiency in a multi-tenant environment and how integrating AWS serverless services with Fauna addresses these complexities. The reference architecture combines elements of siloed and pooled deployment models, providing a balance between meeting isolation requirements and achieving operational efficiency. With its built-in data isolation features and distributed ACID compliance, Fauna complements the serverless architecture by simplifying database operations in a multi-tenant environment. The solution leverages AWS Lambda functions to interact with Fauna's document-relational database, utilizing HTTP for lightweight communication between services. The identity provider uses Amazon Cognito to authenticate users, passing context to Lambda functions and appending it to the Fauna API key to determine which child databases the calling function is authorized to query. Fauna's distributed transaction engine enables multi-region replication by default, allowing customers to easily conform to data residency regulations. The combined approach provides a flexible and secure framework for building serverless multi-tenant and multi-region SaaS applications.