Reliability

When a monolith fails, it tends to fail completely. A database is unavailable, and then the application tries to use stale connections in a connection pool, eventually the threads or processes serving requests lock up, and users are left with a white screen of death or a inoperable mobile application. Microservices allow you to decide on a case-by-case basis how a failure in a particular part of your application should be treated. If your service cannot reach a database, perhaps it's better to return a stale cache, or an empty response. If your service has to throw up its hands and start returning HTTP 503 responses, upstream services can respond by applying back pressure, allowing the service to catch up. Microservices give you much more freedom to isolate failures in your system, resulting in a happier experience for your users.

This book will serve as a handy reference for many of the subjects that will come up as you develop microservices. We'll start with recipes that will help you make the transition from a monolith to a suite of microservices. Subsequent chapters will address specific areas or challenges that come up when choosing how best to architect and manage your microservices. Recipes that cover code will include working, simple, tested examples that you can use in your own applications. My hope is that this book will help you think about, plan, and execute the development of microservice-based applications. Enjoy!