Microservice Architecture Pattern 1 - Decomposition Pattern

Hey there, Welcome to the series of Microservice Architecture Patterns Part-1. In this series of articles, I will be covering all the patterns shortly and conclusively. In this first article, we will go through the initial pattern called Decomposition Pattern.

These patterns help to break down a monolithic application into smaller, more manageable microservices. In detail, we will discuss three decomposition patterns: Decomposition by Business Capability, Decomposition by Subdomain, and Decomposition by Transaction.

1. Decomposition by Business Capability

In this decomposition, we aim to create microservices based on business needs (specific functions or processes an organization performs to deliver value to customers). For example in an e-commerce business, these processes can be login, order management, inventory management, fulfillment, etc.

• Business capability decomposition is ideal when your team understands business units well.
• It suits applications with many interconnected functions or processes, or those prone to frequent changes.
• It aligns application architecture with distinct business units, aiding development and deployment.
• Advantages include improved business alignment, cross-functional teams, and enhanced user experience.

2. Decomposition by Transaction

In transaction decomposition, the system is designed such that each particular transaction belongs to a separate microservice. A transaction, in this context, refers to a series of operations performed between components of the system as a unit of work to achieve a particular business goal.

In this pattern, the components that participate in a transaction are grouped as a part of the same microservice.

When to Use:

• For operations that involve multiple parts or services working together.
• Ideal for frequent and complex transactions, like in e-commerce or finance apps.
• Best suited for situations demanding strict consistency across all involved components.

Advantages:

• Reduced Complexity: Grouping related components makes system development and maintenance easier.
• Minimized Two-Phase Commit Issues: Each transaction in a separate microservice avoids problems, creating a reliable system.
• Reduced Latency: Coordinating transactions within one microservice reduces delays, providing a better user experience.
• Better Alignment with Business Needs: Breaking down the system based on transactions aligns microservices with specific business requirements, making the system more efficient.

Challenges and Issues:

• Potential Monolith Creation: Grouping too much into one microservice may create a monolithic system; focus on keeping each microservice specific to one business domain.
• Increased Cost and Complexity: Handling multiple functionalities in one microservice can raise costs and complexities; avoid this by carefully defining each microservice's scope.
• Incompatible Versions: Deploying different versions of the same microservice may cause errors; manage versioning and deployment processes carefully to ensure consistency.

3. Decomposition by Subdomain

Microservice decomposition by subdomain is a process of breaking down a monolithic system into smaller, independent microservices based on the corresponding subdomains defined by Domain-Driven Design (DDD).

DDD refers to the application's problem space - the business - as the domain, which is comprised of multiple subdomains

When To Use:

• Ideal for large, complex applications with multiple workflows and interdependent rules.
• Well-suited for agile development methodologies, improving time-to-market and reducing costs.
• Enhances scalability by allowing independent scaling of each service.
• Enables flexibility, allowing changes to specific areas without affecting the entire application.

Advantages:

• Improved Scalability and Predictability: Microservices can be scaled independently, providing a stable and reliable system. Faults in one microservice won't affect the rest of the system.
• Loosely Coupled Architecture: Microservices operate independently, offering benefits like scalability, resilience, maintainability, and extensibility. Supports location transparency, allowing deployment closer to users or data sources. Protocol independence facilitates integration with existing systems. Time independence enables development and deployment by different teams without interference.

Challenges and Issues:

• Excessive Microservices Creation: The pattern may lead to the creation of a large number of microservices. This abundance can complicate service discovery and integration, raising complexity and operational issues.
• Identifying Business Subdomains: Requires a deep understanding of the overall business for determining subdomains. Lack of sufficient business knowledge may make it challenging to identify the right subdomains, potentially leading to suboptimal microservice design and implementation.