We start off with a brief introduction to the WWW, concurrency and scalability in chapter 2. We then focus on web architectures in chapter 3 and elaborate a general architectural model for scalable web architectures based on existing systems. Next, we have an isolated look at different stages of this model and get to know their relevant concurrency challenges and available approaches to adopt. This includes web servers in chapter 4, applications and business logic in chapter 5 and backend storages in chapter 6. In chapter 7, we provide a guideline for choosing a decent approach or concept for different scenarios. Next, we discuss the results of our considerations as part of chapter 8 and take a look at the essence of concurrency and scalability in distributed systems. We finally dare an outlook on the near future of web architectures and how it will be affected by new web technologies and programming concepts in chapter 9. The conclusion in chapter 10 sums up our survey on concurrency in web architectures.