Event sourcing is a very popular pattern in modern server systems, helping systems to hold massive traffic. Node.js has become one of the most popular frameworks to write servers in the last few years. As Node servers need to scale up to more and more data, they need to get familiar with architecture patterns that will allow them to scale their server efficiently. In this lecture, after explaining what event sourcing is and in which cases it is good for, I will show several implementations of event sourcing server, starting with implement it yourself, integrate with different event buses and implementing it with the Nest.js, a new Node.js library rising in popularity that has a built-in event-sourcing module. At the end of this lecture, the developers will have knowledge about this pattern, when it fits their project needs and how to implement it.