A Visual Guide to Software Architecture Patterns

Software architecture can be abstract and hard to grasp from text alone. This guide uses diagrams to illustrate common patterns, making it easier to understand when and why to use each approach.

Layered Architecture#

The most traditional pattern, organizing code into horizontal layers with specific responsibilities.

When to use: Traditional business applications, CRUD-heavy systems, teams familiar with MVC frameworks.

Pros: Clear separation, easy to understand, well-documented patterns.

Cons: Can lead to "lasagna code," changes often ripple through layers.

Model-View-Controller (MVC)#

A specialized layered pattern focused on separating data, presentation, and user interaction.

The flow:

1. User sends a request (click, form submit)
2. Controller processes the request, interacts with Model
3. Model returns data
4. Controller selects appropriate View
5. View renders the response
6. Response sent to user

Event-Driven Architecture#

Systems that communicate through events, enabling loose coupling and scalability.

Key concepts:

• Producers emit events without knowing who consumes them
• Consumers subscribe to events they care about
• Event Broker handles routing and delivery guarantees

Microservices Architecture#

Decomposing applications into small, independent services that communicate over a network.

Characteristics:

• Each service owns its data
• Services communicate via APIs or messages
• Independent deployment and scaling
• Technology diversity possible

CQRS (Command Query Responsibility Segregation)#

Separating read and write operations into different models.

When to use:

• Complex domains with different read/write patterns
• High read-to-write ratios
• Need for specialized read models (search, reporting)

Hexagonal Architecture (Ports & Adapters)#

Isolating core business logic from external concerns through ports (interfaces) and adapters (implementations).

Benefits:

• Core logic is isolated and testable
• Easy to swap external dependencies
• Clear boundaries between concerns

Data Flow in a Modern Web Application#

Putting it together—how data flows through a typical modern stack:

Choosing the Right Pattern#

Conclusion#

Architecture patterns are tools, not rules. The best architects understand multiple patterns and know when to apply each one—or when to combine them. Start simple, evolve as needed, and always consider your team's capabilities and your system's actual requirements.

Remember: the goal isn't to use the most sophisticated pattern, but to solve real problems effectively while maintaining code that your team can understand and evolve.