Microservices architecture has gained popularity in recent years as a way to build large and complex applications that can scale and evolve rapidly. Microservices architecture involves breaking down a monolithic application into smaller, independent services that communicate with each other through APIs. Each service performs a specific business function and can be developed, tested, and deployed independently.

The decomposition of a monolithic application into microservices involves several patterns and techniques, such as the subdomain pattern and the business capability pattern. These patterns provide a framework for breaking down the application into smaller, independent services that can be developed and managed more efficiently.

However, decomposing a monolithic application into microservices is not always a straightforward process, and several obstacles must be considered during the design and implementation phase. These obstacles include complexity, data management, service coordination, testing and deployment, and security.

Despite the challenges, microservices architecture offers significant benefits such as increased scalability, flexibility, and agility. A well-designed microservices architecture can help organizations to innovate and respond quickly to changing business requirements.

This article will explore the patterns of decomposition in microservices architecture, including the subdomain and business capability patterns. It will also discuss the obstacles of decomposition and how to address them. Finally, it will highlight the benefits of microservices architecture and why it has become an increasingly popular approach for building large and complex applications.

Decomposition in Microservices Architecture

Decomposition in a microservices architecture is the process of breaking down a monolithic application into smaller, independent services. Decomposition is a complex process that involves analyzing the existing monolithic application, identifying the independent services, defining their boundaries, and creating APIs that allow them to communicate with each other.

The 4+1 Model

The 4+1 model is a popular software architecture design pattern that consists of four logical views and one physical view. The logical views include the user view, the logical view, the process view, and the development view. The physical view provides a mapping between the logical views and the physical components of the system. This model is commonly used in the design and development of software systems, including microservices architecture.

Logical View-

The logical view is the view of the system from a functional perspective. It defines the functional requirements of the system and the relationships between the system's components. The logical view includes the high-level design of the system's components, interfaces, and interactions. It also defines the system's architecture, including the layers, modules, and components.

The logical view defines the structure of the microservices and their interactions with each other. It defines the API contracts between the microservices, which are essential for communication and coordination. The logical view also defines the service boundaries and the granularity of the microservices.

Implementation View-

The implementation view is the view of the system from a software development perspective. It defines the software development artifacts, such as source code, compiled code, and executable files. The implementation view includes the software development tools, the programming languages, and the coding standards.

The implementation view defines the development and deployment processes for the microservices. It defines the programming languages, frameworks, and tools that are used to develop the microservices. It also defines the containerization and orchestration technologies used to deploy and manage the microservices.

Process View-

The process view is the view of the system from a concurrency and synchronization perspective. It defines the system's behavior under different conditions and the interactions between its components. The process view includes the system's processes, threads, and events. It also defines the system's performance and scalability requirements.

The process view defines the behavior of the microservices under different conditions, including high load and failures. It also defines the communication and coordination mechanisms between the microservices. The process view also defines the event-driven and reactive architectures used in microservices.

Deployment View-

The deployment view is the view of the system from a deployment and infrastructure perspective. It defines the deployment and runtime environments for the system's components. The deployment view includes the hardware, software, and network infrastructure needed to run the system. It also includes the deployment topology, such as the number and location of servers and the load balancing configuration.

The deployment view defines the containerization and orchestration technologies used to deploy and manage the microservices. It defines the deployment topology, such as the number and location of containers and the load balancing configuration. It also defines the monitoring and logging infrastructure needed to ensure the health and performance of the microservices.

The 4+1 model provides a comprehensive framework for designing software architecture, including microservices architecture. The model's logical views provide a functional perspective, while the implementation view provides a software development perspective. The process view provides a concurrency and synchronization perspective, while the deployment view provides a deployment and infrastructure perspective. The physical view maps these views to the physical components of the system, making it easier to understand the system's behavior and interactions.

Patterns of Decomposition-Subdomain and Business Capability

The patterns of decomposition in a microservices architecture are essential for breaking down a monolithic application into smaller, independent services. Two popular patterns of decomposition are the subdomain pattern and the business capability pattern.

Subdomain Pattern: The subdomain pattern involves breaking down the application based on different subdomains. In this pattern, each subdomain represents a unique domain of the business. For example, an e-commerce website could have subdomains such as product catalog, shopping cart, payment gateway, and order management. Each of these subdomains can be implemented as a separate microservice. The subdomain pattern is suitable for applications where each subdomain requires a different approach to data management, security, and scalability. For example, the payment gateway subdomain may require more stringent security measures than the product catalog subdomain.

Business Capability Pattern: The business capability pattern involves breaking down the application based on different business capabilities. In this pattern, each service represents a specific business capability. For example, an e-commerce website could have services such as search, recommendation, payment, and customer management. Each of these services can be implemented as a separate microservice. The business capability pattern is suitable for applications where each business capability requires a unique approach to the user interface, functionality, and performance. For example, the search service may require a different approach to performance optimization than the payment service.

Both the subdomain and business capability patterns have their advantages and disadvantages. The subdomain pattern provides a clear separation of concerns and allows for better data management, security, and scalability. However, it may result in more complex service coordination and communication. The business capability pattern provides a clear separation of business capabilities and allows for better user interface, functionality, and performance. However, it may result in a less clear separation of concerns and data management challenges.

Both the subdomain and business capability patterns of decomposition are essential for designing microservices architecture. The choice of the pattern depends on the specific requirements of the application and the trade-offs between separation of concerns, service coordination, and data management. A well-designed microservices architecture can provide significant benefits such as increased scalability, flexibility, and agility.

Obstacles of Decomposition:

Decomposing a monolithic application into microservices is not always a straightforward process, and several obstacles must be considered during the design and implementation phase. Some of the common obstacles of decomposition in a microservices architecture are:

Complexity: Decomposing a monolithic application into smaller services can be a complex and time-consuming process, especially if the application is large and complex. Designing a microservices architecture involves analyzing the existing monolithic application, identifying the independent services, defining their boundaries, and creating APIs that allow them to communicate with each other. This process requires a deep understanding of the application and its business logic.
Data Management: Breaking down an application into smaller services can create data management challenges, as each service has its database. This can lead to data duplication, inconsistency, and synchronization issues. Managing data in a microservices architecture requires a well-defined data access strategy and careful consideration of data ownership and sharing.
Service Coordination: Breaking down an application into smaller services requires effective service coordination and communication between services. This can be a challenging task, especially when dealing with complex business processes that span multiple services. Service coordination requires a well-designed API architecture, service discovery, and load-balancing mechanisms.
Testing and Deployment: Testing and deploying a microservices architecture can be more challenging than testing and deploying a monolithic application. Each service must be tested and deployed independently, which requires a well-designed testing and deployment strategy. This can lead to more complex testing scenarios, especially when testing the interactions between services.
Security: Breaking down an application into smaller services can create security challenges, as each service has its security requirements and vulnerabilities. Ensuring the security of a microservices architecture requires a well-defined security strategy and careful consideration of security risks and threats.

Microservices architecture offers several benefits such as increased scalability, flexibility, and agility. However, designing and implementing a microservices architecture is not always a straightforward process, and several obstacles must be considered. Addressing these obstacles requires a deep understanding of the application, its business logic, and the specific requirements of the microservices architecture.

Conclusion-

Decomposition in a microservices architecture is a critical process that involves breaking down a monolithic application into smaller, independent services. The 4+1 model is a popular approach for designing microservices architecture, and there are two popular patterns of decomposition, namely subdomain and business capability. However, there are several obstacles to decomposition, such as complexity, data management, and service coordination, that must be addressed to ensure the success of the microservices architecture.

References-

microservices.io

Breaking it Down: Understanding the Patterns, Obstacles, and Benefits of Microservices Decomposition