Ever been in a design meeting where someone draws a high-level architecture on a whiteboard, and by the end, it looks more like an ancient treasure map than a system diagram? 🤯 One person draws boxes labeled "Microservices" and "DB", while another sketches some arrows that somehow represent real-time, async, and batch processing all at once.
Then, a product manager walks in and asks, "But where is the business logic?"
— and that’s when the architect decides it's time for coffee. ☕
Software design often turns into a guessing game where different stakeholders see the system from different angles—developers worry about implementation, architects think in patterns, product managers want business clarity, and clients just want to know, "Will this work?" 🤔
This is where the C4 Model saves the day! 🦸♂️
1️⃣ What is the C4 Model?
The C4 Model is a set of hierarchical diagrams (Context, Container, Component, Code) and provides a structured way to visualize and describe software architecture. It helps to bridge the communication gap between technical and non-technical teams, providing clarity on both the big picture and the nitty-gritty. It's widely used for system documentation, architecture design and to analyze dependencies, internal and external integrations.
2️⃣ Breaking it Down: The Four C’s
✅ Context Diagram – The "Big Picture"
What does the system do?, Who uses the system and why?
High-level overview of the system and its interactions with users and external systems.
Audience: Business, Architect, Product, Developer
Example (Google Maps Context)
Users:
- End users (regular users using the mobile or web app)
- Businesses using Google Maps API for location services
- Delivery services (Uber Eats, DoorDash) integrating Maps
External Systems:
- Google Search (for place lookups)
- Google Places API (for location-based business details)
- Google Cloud (for data storage, compute services)
- Payment services (Google Pay for ride-hailing, parking, toll payments)
✅ Container Diagram – The high-level building blocks
What are the main applications or services?
Helps us see how the system is set up and how it works with other integrations (Web App, Mobile App, DBs, Cache, Cloud, etc.)
Audience: Architect, Product, Developer
Example (Google Maps Containers)
Frontend (Mobile/Web Apps)
- Google Maps Mobile App (Android/iOS)
- Google Maps Web Application
Backend Services
- Maps Data Service (stores roads, buildings, locations)
- Routing Service (handles navigation, traffic updates)
- Geolocation Service (converts latitude/longitude to addresses)
- Street View Service (provides street-level images)
- Google Places API (fetches restaurant, hotel, gas station data)
- Traffic Analysis Service (integrates real-time traffic, historical trends)
Storage & Infrastructure
- Google Cloud Storage (for map tile data, cached locations)
- BigQuery (to process location-based data)
- Firebase (syncs real-time data for mobile apps)
✅ Component Diagram – The internals of a container
What components/modules exist in application / service?
Overview of specific parts doing specialized jobs
Audience: Architect, Developer
Example (Google Maps Routing Service)
- Route Calculation Module: Finds shortest path using algorithms like Dijkstra’s/A*.
- Traffic Predictor: Uses historical + real-time data to estimate delays.
- Alternative Route Finder: Suggests different routes.
- User Location Service: Tracks real-time movement.
- Third-Party Data Integrator: Fetches public transit, ride-hailing data (Uber, Lyft).
✅ Code Diagram – Zooming in on implementation details
At the code level, we describe the logic of a single component
Audience: Developer, Designer
Example (Google Maps Routing Code)
- RouteController.java (exposes REST API)
- RouteService.java (business logic for computing routes)
- TrafficAnalysisService.java (predicts delays)
- GraphProcessor.java (Dijkstra’s algorithm implementation)
- GoogleMapsDB (stores precomputed routes for performance)
Each level helps different people get the information they need—without unnecessary complexity.
3️⃣Audience Perspectives: How Different Stakeholders See the C4 Model
💰 Clients/Business Owners: "As long as it doesn’t crash, Add values to customer and 💵 /💲I’m happy :)"
📈 Product Managers: "So this is how our product actually works?!"
🏗️ Architects: "Finally, a structured way to describe systems across teams!"
👨💻 Developers/Designers: "Ah, now I know which service calls what and where my code/design fits!"
4️⃣Why C4 Model is Better Than Chaos
- No more ambiguous arrows.
- No more lost in UML nightmares.
- Consistent design across suites of products and teams.
- Common nomenclature for technical and non-technical audience.
5️⃣Real-World Example: C4 Model in Action
Please review a short case study of architecture diagram using C4 and Google Maps.
6️⃣Best Practices for Using the C4 Model
- Works across any language, framework, or platform, making it universally applicable.
- Maintain consistency across teams.
- Simplifies Complex Systems.
- Supports Agile Development.
- Facilitates Onboarding
- Adjust details based on the audience.
Final Thoughts
Next time someone asks you to "just sketch the architecture real quick," resist the urge to draw random boxes and arrows. Instead, use the C4 Model to keep things clear, structured, and (most importantly) understandable!
What do you think? Would you like me to expand on any section? 😊. Let me know in comments. Thanks
References
A huge thanks to the online documentation, contributors, community and all the resources available that made this write-up possible.
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