Making Sense of Software Architecture with the C4 Model

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Ever tried explaining your system architecture and ended up drawing a bunch of rectangles that confused everyone, including you? Yeah, same.

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That’s where the

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comes in, it’s like Google Maps for your codebase.

Zoom in, zoom out, show only what matters, and skip the fluff.

Let’s break it down, dev-to-dev.

Why Should You Care?


Because "drawing boxes and lines" isn't enough.

Diagrams should communicate, not decorate.

Whether it’s onboarding a new hire, defending your architecture in a review, or just making sense of a spaghetti monolith, you need clarity.

C4 is:

• Notation-agnostic (use boxes, colors, ASCII art—your call)
• Tooling-independent (draw on paper, use diagrams.net, Structurizr, etc.)
• Easy to learn (no need to memorize UML specs)
• Focused on abstractions and levels of detail

Level 1: A system context diagram provides a starting point, showing how the software system in scope fits into the world around it.	Level 2: A container diagram zooms into the software system in scope, showing the applications and data stores inside it.	Level 3: A component diagram zooms into an individual container, showing the components inside it.	Level 4: A code diagram (e.g. UML class) can be used to zoom into an individual component, showing how that component is implemented at the code level.

The 4 Levels in C4 (Context, Containers, Components, Code)


Think zoom levels. Each level answers a different question.

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Level 1: System Context Diagram


What are we building and who/what interacts with it?

• Show your system as a box.
• Surround it with people, APIs, 3rd-party services, etc.
• Useful for: stakeholders, managers, onboarding slides.

?"This box is us. These are the folks and systems we talk to."

Level 2: Container Diagram


What’s inside our system?

"Container" doesn’t mean Docker here, it’s a runtime unit like:

• Web apps
• Mobile apps
• Databases
• APIs
• Background services
• Blob stores

You're breaking down the system into deployable units.

? Think of it as "how we ship and run stuff."

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Level 3: Component Diagram


What are the building blocks of a container?

If your Node.js app is a container, then:

• Each route handler + business logic module = component
• You show internal structure: controllers, services, utils, etc.

This is super helpful for fellow devs, especially in layered or hexagonal architectures.

?️ "Here's what’s inside this box, grouped by logic, not files."

Level 4: Code (Optional, Zoomed-In View)


Want to go full nerd? Here's the code-level diagram.

UML class diagrams, interfaces, functions—basically your IDE in diagram form. But this level is often skipped unless you're:

• Documenting a library
• Teaching internal architecture
• Auto-generating diagrams from code

? "Here’s the guts of that service, class by class."

It’s All About Abstractions


Let’s clarify the C4 abstractions:

• Software System: The whole thing you’re building (like “LiveAPI”). Think team-level responsibility.
• Container: Something running (BE, DB, frontend app, etc).
• Component: Logical chunks inside a container (routes, services, handlers).
• Code: The actual classes, functions, modules, etc.

Common Mistakes C4 Helps Avoid


Mixing abstractions (e.g., putting low-level tech in a system diagram)
Unlabeled arrows (seriously, what does this line even mean?)
Random colors and styles with no legend
Overloaded terms like “service”, “module”, “component” without context

? Tools You Can Use (But Don’t Have To)

• 
  

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  – Text-based C4 diagrams
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• 
  

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• Pen and paper – Seriously, it’s fine

The model is tool-agnostic on purpose.

Final Take


C4 isn’t about pretty diagrams. It’s about shared understanding.

• Junior devs get context faster.
• Seniors reason about dependencies and risks better.
• PMs and architects don’t get lost in classes and configs.

Think of it as version-controlled, zoomable documentation.

TL;DR

• C4 = 4 zoom levels of architecture (Context → Container → Component → Code)
• Keep diagrams clear, labeled, and audience-appropriate
• Great for onboarding, audits, incident reviews, threat modeling
• You don’t need fancy tools, just a consistent approach

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I’ve been actively working on a super-convenient tool called LiveAPI.

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helps you get all your backend APIs documented in a few minutes

With LiveAPI, you can quickly generate interactive API documentation that allows users to execute APIs directly from the browser.

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If you’re tired of manually creating docs for your APIs, this tool might just make your life easier.

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