Choosing the Right Software Architecture: WHEN to use WHAT & WHY

This is a follow-up to our previous article, where I explained some of the most common software architectural styles. I previously talked about the introduction level of the most frequently used software architecture styles, which you can read from the link if you haven't already. In this article, I'll go a step further and explain when and why you should apply each style.

To make things easier, the table below ranks each architectural style based on the factors that influence how they perform. Every characteristic has been evaluated on a scale of 1 to 5, with 1 representing a low score (e.g., limited or basic capabilities) and 5 representing a high score (e.g., great performance or suitability).

Let's learn about every characteristic first, and then we'll get further into each type.

• Cost: Is a measures of financial investment required for development, deployment, and maintenance of the architecture
• Maintainability: Evaluates how easy it is to update, fix, or improve the architecture over time
• Testability: Refers to how easily the architecture can be tested for functionality and bugs
• Deployability: Determines the ease and flexibility of deploying the application made by adopting a certain architecture
• Simplicity: Shows how easy the architecture is to understand and implement
• Scalability: Assesses how well the architecture can handle increased workloads
• Elasticity: Reflects the ability to adapt to changes in demand, such as scaling up during high traffic for each architecture
• Responsiveness: Indicates how quickly an architecture reacts to inputs or events
• Fault-Tolerance: Measures the architecture’s ability to continue operating even if some parts fail
• Evolvability: Highlights how easily the architecture can adapt to changes or new requirements
• Abstraction: Refers to the clarity and separation of concerns within the architecture
• Interoperability: Reflects how well the architecture can interact with other systems or components

Layered Architecture

Layered architecture scores highly on simplicity (5/5) because it’s straightforward and easy to understand. However, it scores low in areas like scalability (1/5), fault-tolerance (1/5), and evolvability (1/5), making it unsuitable for complex or rapidly changing systems. It’s also not very responsive (2/5) or elastic (1/5), which means it struggles to handle high loads or real-time demands.

When to Use: It’s best for small, structured applications that don’t need frequent updates or handle high traffic.

Example: A school’s student management system where users can log in, view grades, and access study materials. This simple structure doesn’t require scalability or advanced features.

Modular Monolithic Architecture

This architecture strikes a balance between simplicity (4/5) and maintainability (2/5). It improves testability (2/5) and evolvability (2/5) compared to layered architecture, making it easier to manage updates. However, it still falls short in scalability (2/5), elasticity (2/5), and fault-tolerance (1/5), so it’s not ideal for very large systems.

When to Use: Use this for medium-sized projects where some modularity is needed but full scalability is not a priority.

Example: A company’s HR system that handles payroll, leave requests, and employee performance. Each feature is modular but remains part of a single application.

Microkernel Architecture

Microkernel architecture balances many characteristics well, scoring moderately on scalability (3/5), fault-tolerance (2/5), and elasticity (3/5). It also rates highly for maintainability (3/5), testability (3/5), and evolvability (3/5), making it a good choice for systems that require a core set of features with optional extensions.

When to Use: Ideal for applications that need flexibility and extensions over time.

Example: A graphic design tool like Canva, where the core application is lightweight, and users can add plugins for specific features.

Microservices Architecture

This architecture scores very well in scalability (4/5), elasticity (4/5), and evolvability (4/5), making it a great choice for modern, distributed systems. It also scores high in maintainability (4/5) and testability (4/5), as each service can be developed, tested, and deployed independently. However, simplicity is lower (2/5), and it can be costly to implement (3/5).

When to Use: Use this for large, complex systems where scalability and independent updates are the key elements.

Example: An e-commerce platform like Amazon, where different services (e.g., payments, inventory, and accounts) operate independently for seamless functionality.

Service-Oriented Architecture (SOA)

SOA offers strong interoperability (4/5), maintainability (4/5), and evolvability (4/5). It’s designed for enterprise environments where multiple services need to work together. While it’s scalable (4/5) and fault-tolerant (4/5), it’s less simple (2/5) and can be more expensive to implement (4/5).

When to Use: Ideal for large organizations that need to integrate multiple systems.

Example: A bank’s IT system connecting services for loans, account management, and fraud detection while ensuring they can work together.

Event-Driven Architecture

Event-driven architecture scores very high in scalability (5/5), elasticity (5/5), and fault-tolerance (5/5). It’s designed for responsiveness (5/5), making it suitable for systems that need to react in real-time. While it’s less simple (2/5), it offers excellent evolvability (5/5) and interoperability (5/5).

When to Use: Use this for systems where real-time event processing is critical

Example: A smart home system where devices like lights and alarms respond instantly to motion detection or temperature changes

Space-Based Architecture

Space-based architecture is a powerhouse for scalability (5/5), elasticity (5/5), and fault-tolerance (5/5). It’s designed to handle high traffic and low latency. While it’s less simple (2/5) and costs more to implement (4/5), it ensures systems remain responsive (4/5) under heavy load.

When to Use: Ideal for applications with unpredictable, high traffic.

Example: An online multiplayer gaming platform where thousands of players interact without delays or crashes.

Conclusion

One of the most critical decisions when developing software or online apps is selecting the right architecture. Each architectural style has advantages and disadvantages, and it performs best in certain environments.

In this post, I had examined many architectural styles, their positive and negative aspects, and the particular settings in which they excel. Making the right choice is critical because the architecture you select impacts how scalable, maintainable, and cost-effective your system will be. A poor choice can lead to problems down the road, but picking the right one ensures that your solution is strong, dependable, and future-ready. Choose wisely!