Welcome to the book "Angular Observables and Promises: A Practical Guide to Asynchronous Programming". In this book, I explain how to use observables and promises effectively for asynchronous programming. I show you practical scenarios and explain when you should use them and which operators you need to use. I will give you best practices with important pointers that, when used correctly, can make all the difference and have a big impact on performance. There are also things you should be aware of and avoid when working with observables, otherwise performance can be affected. By the end of this book, you will be able to use Observables and Promises in your Angular application and handle all kinds of scenarios. Let us get started.