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Queuing Theory for Software Engineers

“Start With Why”

Queues are a built-in mechanism everywhere in today's software. Not being familiar with the basics of queuing theory will prevent you from understanding the relations between latency and throughput, high-level capacity estimations, and workload optimization. Knowing the internals of queuing models is actually not that hard to grasp. In this article, I'll sum up the essence of what's required for a software engineer to be more effective in their field.

Queues Are Everywhere!

Let's see some common examples from an average dude's vocabulary (like me). I'll list some of the technology usages of queues without even thinking about it.

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Protect Your Invariants!

How do you handle constraints and validation inside your application? Most developers put this logic somewhere close to their application's boundary. Actually, this prevents them from having a rich domain model that could ensure consistency.

Developers tend to get confused when they need to find a good place for their business logic. I suspect that most probably the reasons are related to all those bad examples circulating in the documentations of popular frameworks and bad habits from coding in old-fashioned enterprise platforms like J2EE. Most of the time, they're afraid to keep these vital pieces of information in the language elements most relevant to the target domain: I'm talking about the simple classes reflecting the "nouns" of the business logic. Often, you see something like the example below: