Microservice architecture vs modular architecture

---

Architecture is the bearing structure of your project, and it can make or break it. Why? Because it forms the foundation for a system’s performance, scalability, and maintainability. But there are numerous approaches, and a few that do really stand out. Modular architecture and microservice architecture are those that do, and will fit according to your project. 

The question is choosing one or the other. This article explores the differences and similarities between the two, which will hopefully assist you in making your decision. Whether you’re aiming for rapid deployment and scalability or prefer a more centralised and integrated approach, understanding these architectures will help you make the best decision for your project.

Let’s start with the basics.

What is microservice architecture?

It is a design approach where it involves creating a software application out of small, independent services that communicate over well-defined APIs. Each service in it focuses on a specific business function and can be developed, deployed, and scaled separately, and independently.

Here are its key characteristics:

• Decentralised data management: Microservices manage their own databases, promoting data autonomy and lowering dependency.
• Independently deployable services: Services can be updated, scaled, and deployed separately from each other, which helps you raise agility.
• Loose coupling and high cohesion: Services are loosely coupled but very cohesive. This makes sure that changes in one service do not impact others too much.

What is modular architecture?

It is all about dividing a software system into modules, each of which is responsible for a specific functionality. But also forming a cohesive whole. Different to microservices, modules are not standalone services but parts of a larger application.

Here are it’s key characteristics:

• Centralised data management: Modules usually share a central database for consistent data management.
• Modules as part of a larger application: They operate within the context of a single application, allowing for integrated functionality.
• Tight coupling within modules but loose coupling between modules: Modules are tightly coupled internally but interact with each other through well-defined interfaces.

Comparison criteria

Scalability

This factor is very important in evaluating an architecture’s ability and capability of managing increasing loads and expanding demands when you need it to. It makes sure the system can scale efficiently without making performance worse. This criterion emphasised the distinct scaling methodologies used by each architecture:

Microservices:

• Horizontal scaling: The microservice can be easily added because of the design of the architecture. 
• Independent scaling of services: Each service can be scaled based on its specific load, for optimised performance.

Modular architecture:

• Vertical scaling: It involves enhancing the overall system’s resources, which can be a bit more restrictive.
• Scalability limitations: Compared to microservices, modular architecture can encounter limitations in efficiently scaling specific modules.

Flexibility

The ability to accommodate changes and integrate new requirements or technologies without extensive rework in this case is called flexibility. It is very important for adapting to evolving business needs and technological advancements.

Microservices:

• Technology stack independence: Every and each service can use different technologies best suited for its functionality.
• Easy adoption of new technologies: New tech can be integrated without affecting the entire system.

Modular architecture:

• Consistency in technology stack: A uniform technology stack makes development and maintenance much simpler.
• Challenges in integrating new technologies: Introducing new technologies can be complex and affect the whole entire system.

Performance

In this line of work you need to know how quickly and efficiently a system processes tasks. It is key for pushing user satisfaction and system efficiency. We compare the impact of communication methods:

Microservices:

• Network latency concerns: Communication between services over a network can actually introduce latency.
• Service-to-service communication overhead: The overhead of inter-service communication can have an impact on the overall performance.

Modular architecture:

• Lower network latency: Modules communicate directly, lowering latency. 
• Direct module communication: Eliminates the overhead tied with network communication.

State Management / State Consistency

The way how an architecture handles data consistency and synchronization across the system is evaluated by state management, which you need to promote reliable operation and data integrity, most useful in distributed environments.

Microservices:

• Complexity in distributed systems: Needs managing state across distributed services, often using complex protocols for consistency.
• Independent state management: Each microservice can manage its own state, which lowers unintended side effects but increases orchestration complexity.

Modular architecture:

• Centralised state management: Typically manages state in a centred way, which makes consistency and integrity easier to maintain.
• Simpler transactions: State updates and transactions are straightforward, making complexity and potential errors less likely to happen.

Development complexity

It is difficult to manage a system but even this has levels to it and development complexity is the metric for that. It mainly affects project timelines and the way you split up resources, but as it is a part of a foundation it will eventually have an effect on all aspects of your project.

Microservices:

• Managing multiple services: Needs sophisticated tools and practices to manage numerous services.
• DevOps and CI/CD pipeline requirements: Continuous integration and deployment processes are very important to managing microservices efficiently.

Modular architecture:

• Single codebase management: Easy to manage a unified codebase.
• Simpler build and deployment processes: The development cycle is straightforward, with not so many moving parts.

Maintenance & updates

How easily the system can be maintained and updated over time is a very important aspect for longevity. It is crucial for making the ground for long-term reliability and up-to-date functionality of the system.

Microservices:

• Independent service updates: Services can be updated independently without affecting the entire system.
• Versioning and backward compatibility: You need careful versioning to ensure service compatibility.

Modular architecture:

• Centralised updates: Updates can be rolled out centrally but may affect the whole system.
• Potential impact on entire system: Changes in one module can have broader impacts.

Cost considerations

Another key side of any project is the financial impact of implementing and maintaining the architecture. All the budget planning and resource allocation is affected by cost considerations. The initial and long-term costs are like this:

Microservices:

• Infrastructure costs: Higher costs because of the need for multiple deployment environments.
• Monitoring and management costs: Higher complexity increases monitoring and management costs.

Modular Architecture:

• Lower initial costs: Simpler setup can lower initial investment.
• Potential long-term maintenance costs: Centralised management can make maintenance costs higher over time.

So, when to use microservice architecture?

Microservice architecture is great for:

• Businesses that need high scalability like as e-commerce platforms and cloud services.
• Large organisations, where designing, developing, maintaining, and especially reusing microservices is easier, bettering team autonomy and streamlining complicated development processes.

Big companies such as Netflix, Amazon, and Spotify already use microservices to make their system’s more robust for flexibility and scalability.

And, when to use modular architecture?

Modular architecture suits:

• Enterprise applications: Where centralised data management is important.
• Projects, where a stable and consistent technology stack is preferred.
• Examples: Traditional banking systems and large-scale CRM software.

Wrapping up

The way you choose between microservice and modular architecture will always depend on your specific project requirements.  Recap: microservices offer scalability and flexibility but come with increased complexity and costs. Modular architecture brings simplicity and centralised management, which is much better for projects with stable requirements. Of course, I would always recommend getting analytical about goals and project specifics and then seeing which approach applies more and will bring the best result possible.