Mastering Microservice Splitting: 6 Essential Design Principles

Microservice splitting is the process of breaking a large application into independent services. When performing this split, six key principles should be considered.

Single Responsibility Principle

Each microservice should focus on a clearly defined business domain or function, not multiple unrelated features.

Benefits include easier maintenance, reduced coupling, and clearer team responsibilities.

When a service handles a single responsibility, its codebase remains independent, making updates or additions less risky for other services.

Appropriate Granularity Principle

There is no fixed standard for how "micro" a service should be; overly small services can lead to an explosion in the number of services, creating management challenges.

Therefore, services should be split gradually and evolve continuously, avoiding a sudden surge in service count.

Interface Segregation Principle

Define service interfaces to be simple and focused, avoiding unnecessary functionality that increases coupling.

Clear, isolated interfaces hide internal implementation details, allowing independent development, testing, deployment, and continuous delivery of each service.

Avoid Impacting Product Principle

Service decomposition should proceed alongside product feature iteration, starting with independent boundary services (e.g., SMS service) to minimize disruption.

This approach reduces the impact on existing business logic and gives teams a chance to practice and learn from mistakes.

Scalability Principle

Each service should be independently scalable to meet varying load demands.

Since services communicate over the network after being split, interfaces must be designed for extensibility to avoid breaking changes.

Encapsulating parameters in objects allows adding fields without changing method signatures, supporting seamless evolution.

Fault Tolerance Principle

Design services with fault tolerance in mind to prevent single points of failure from collapsing the entire system.