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It protects. It also promotes and prevents.

I sometimes get asked to review, or “comment on”, the architecture for an app. Often the app already exists, and the architecture documentation consists of nothing more than the source code and the folder structure. Sometimes the app doesn’t exist, and the architecture is a collection of hopes and dreams expressed on a whiteboard. Very, very rarely, both exist.

To effectively review an architecture and make recommendations for improving it, we need much more information than that. We need to know what we’re aiming for, so that we can tell whether the architecture is going to support or hinder those goals.

We start by asking about the functional requirements of the application. Who is using this, what are they using it for, how do they do that? Does the architecture make it easy for the programmers to implement those things, for the testers to validate those things, for whoever deploys and maintains the software to provide those things?

If you see an “architecture” that promotes the choice of technical implementation pattern over the functionality of the system, it’s getting in the way. I don’t need to know that you have three folders of Models, Views and Controllers, or of Actions, Components, and Containers. I need to know that you let people book childrens’ weather forecasters for wild atmospheric physics parties.

We can say the same about non-functional requirements. When I ask what the architecture is supposed to be for, a frequent response is “we need it to scale”. How? Do you want to scale the development team? By doing more things in parallel, or by doing the same things faster, or by requiring more people to achieve the same results? Hold on, did you want to scale the team up or down?

Or did you want to scale the number of concurrent users? Have you tried… y’know, selling the product to people? Many startups in particular need to learn that a CRM is a better tool for scaling their web app than Kubernetes. But anyway, I digress. If you’ve got a plan for getting to a million users, and it’s a realistic plan, does your architecture allow you to do that? Does it show us how to keep that property as we make changes?

Those important things that you want your system to do. The architecture should protect and promote them. It should make it easy to do the right thing, and difficult to regress. It should prevent going off into the weeds, or doing work that counters those goals.

That means that the system’s architecture isn’t really about the technology, it’s about the goals. If you show me a list of npm packages in response to questions about your architecture, you’re not showing me your architecture. Yes, I could build your system using those technologies. But I could probably build anything else, too.

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