Modern web applications increasingly require us to move from static web content to a more dynamic paradigm where a lot of integration happens in the background and the user interaction is more and more sophisticated. At the same time, the provided online services need to adapt to the changing business requirements and scale to elastic loads, that is, handling peak hour traffic. Finally, in addition to the service they provide, web applications now tend to collect extra information concerning user interaction to better understand customer behavior. In this chapter, we are going to tackle the following topics: