Serverless architecture, while still a small field, has continued to grow as a topic of interest in software development. Some serverless architectures are now becoming highly complex, powering massively scalable applications that deliver business value across domains. As serverless architecture advances in complexity, it presents unique challenges that aren't really present in other approaches, or if they are present, they are hidden by the other, more major issues that plague those approaches. This book will give you a pragmatic, rational, and experience-based approach to architecting your serverless solution to minimize issues and maximize scalability.

Let's first define Serverless. The current working definition of serverless that's defined in this book is as follows: "A service that abstracts away all server details, provides reactive scaling to demand, and is charged on a resource-usage-based payment model". This encompasses serverless databases and takes into account reactive scaling. Serverless fits use cases from simple web applications to massively scaled and complex applications with millions of users. This book will help you build from a simple web application (with the capability to scale to millions of users with no extra effort from the developers) to a complex application, thus utilizing security, observability, queuing, and caching.

Incorporating serverless components in other styles of architecture is relatively straightforward—for instance, it is easy to use a Function-as-a-Service as a simple replacement for a RESTful API. This approach generally works well, and you can gain large advantages by doing this. To fully realize the benefits of serverless, however, a complete serverless architecture is needed. Building one of these once will also change the way you think about application architecture, meaning that even if you have requirements that demand a non-serverless component, you can still keep the rest of the architecture serverless-first. The components that are covered in this chapter are Function-as-a-Service (FaaS), the Serverless Database, and the Serverless Website. Other components that will be covered later are queues, event hubs, authentication services, and monitoring and logging services.