This book aims to give a practical guide to developing and scaling a Ruby Rails application with a focus on mobile devices and the issues with using a Single Page Application (SPA). Websites are getting more and more traffic from mobiles devices that it has become important to prioritise development to mobilise your web page, even for sites which also have native apps. We will cover enough Ruby Rails to get started and some advanced topics to give you an overview of the language capabilities. It is a practical guide but some wider concepts will be discussed so you have a view of issues when deciding the best architecture to use and general programming tips. For a startup some tips such as focusing on the minimum viable product and suggestions for deciding your technology stack. As a full stack developer people need to be aware of the full product cycle including UX, development, deployment and even big data analysis. How do we prevent our app growing into one large monolithic mess of code, and how microservices can help decouple failure from other components. Here is aquestion when you start building the front end: "SPA orstandard Rails?" some points to consider are: SEO considerations, Caching, logging, and debugging."