Author: Hossein Naderi

Message-passing applications are one of the main components of reliable distributed systems; above all, they make it feasible to decouple the "when" and "where" of a problem from "who does it how." Event-driven applications go one step further and give you the causal chain of your system as a first-class citizen.

While the difference between an event-driven system and one that’s not event-driven is pretty clear and obvious to most software engineers, there are a gazillion ways to design such a system. Each has its own trade-offs and is useful in a specific context. The one I’m going to talk about in this article is modeling applications as state machines that compose and form a fractal-like structure — as each component is an application, and composed ones are also the same kind of application.

Knowing anti-patterns and pitfalls is often more useful than knowing patterns when designing a system, so I decided to write this blog post about factors that I think will lead to producing unreliable systems from my experiences in designing (mostly) distributed enterprise applications.
I’ll be pleased to know your related experiences and comments on the matter.

What Is Modeling?

The human brain is a pattern-seeking device. However, it’s a costly process, and the main goal of thinking is to terminate/resolve what caused this process to start in the first place; so it has developed several mechanisms to prevent it from happening too often; the one related to our discussion here is the mental model. Reality is complex, chaotic, and too messy for our limited brain capabilities and resources to comprehend as it is (if that’s even possible); so our minds will try to create an alternative reality which is very simple and (most of the time) easily understandable, and that’s what modeling is all about! from how we think about how nature works, in science for example, to proper social behavior, to what to be afraid of or seek for, all are the results of our mental model. It is noteworthy that models are neither objective reality nor meant to be so!