Stateless distributed systems are much easier to design, build and scale, compared to stateful ones.

The main reason for this is that we consider all the nodes (e.g., servers) of a stateless system identical. This makes it a lot easier for us to balance traffic between them, and scale by adding or removing servers.

However, stateful systems present many more challenges. As different nodes can hold different pieces of data, they require additional work. They need to direct traffic to the right place and ensure each instance is in sync with the others.

As a result, some of the course’s examples include stateless systems. However, the most challenging problems we cover in this course mainly concern stateful systems.