Especially scale-out systems, but also more traditional, highly available systems need a fault tolerant application design, because the standard fault tolerance mechanisms on infrastructure level are either not available or not sufficient and therefore must be implemented on application level. On the other hand fault tolerance is known as an extremely complicated and challenging domain.
So, time to panic? No, not at all! Even though fault tolerant application design is not a trivial domain but there are a lot of patterns which will give a lot of value while being implemented surprisingly easy. You will learn some of these patterns and how to implement them based on real-life code examples. Those patterns are always extremely useful, also outside the domain of scale-out applications. Yet, very often they do not become implemented, simply because no one knowns how easy it is.