Design Principles

Microservices architecture has become the popular choice for modern application development. While it addresses some issues, it is not a silver bullet. There are disadvantages, and numerous challenges need to be addressed when using this architecture. This necessitates understanding and solving common patterns in these problems with reusable solutions. Therefore, discussing design patterns for microservices is essential. Before diving into design patterns, we need to understand the principles on which microservices architecture is built:

Decentralization

Decentralization refers to not being centralized. In the world of software architecture, it means not being tied to a single center, distributing responsibilities.

It implies that all tasks in the system will not be managed and controlled by a single center.

According to this principle, regardless of the technology a microservice uses, it should have a single responsibility and its own individual management plan.

In microservices-based applications, decentralization should occur in all aspects, from data management to the execution of workflows. This principle emphasizes that microservices should exhibit a high degree of independence in data, development, operational tasks, or team collaborations.

Loose Coupling

This design principle, as mentioned in SOA, states that services should be implemented with the least dependency or ideally no dependency between services. It is the opposite of tight coupling.

For example, in object-oriented programming, consider a class whose object is created in another class. If making changes in one class requires changes in the other class, tight coupling exists.

Autonomy

Microservices take full responsibility for a specific task and work entirely independently for that task. They should have complete control for providing a service and must fulfill the service without dependencies. An autonomous service performs its task by publishing its own API/protocol.

Another aspect of autonomy is that all information needed to address error scenarios should be available within the service, eliminating the need for additional communication and coordination.

This principle also liberates teams from dependencies on the entire lifecycle and operational aspects of the software they produce.

Additionally, services are independent in terms of the technology and infrastructure used for software development.

Isolation of Failures

Isolation means that multiple transactions can run independently of each other without interference. It ensures that any interim state changes made during a transaction are not visible to other transactions.

One of the fundamental features of microservices architecture is the isolation of components and capabilities from each other. If one microservice fails, the rest should continue to operate without being affected until the faulty service is operational again.

This principle emphasizes that failures should be addressed separately. The failure of one service should not impact other parts of the application.

Independent Deployability

An essential principle of microservices architecture is independent deployability. It states that each microservice within an application should be deployable separately.

Independent deployability ensures that updates can be deployed in one service without having to change anything else, maintaining loose coupling. Making each service deployable independently allows for ease of scaling only the necessary components. It saves time and resources.

Scalability

This principle is crucial in deciding whether microservices architecture should be used. Scalability, in short, refers to the system's capacity and capability to increase or decrease its capacity and capabilities according to its performance, load, or other factors.

This principle simply states that each microservice and the tasks they perform should be scalable. Independence of each task makes it easy to scale only the required components. It saves time and resources.

Monoliths limit scalability. The usual strategy to accommodate an increase in incoming requests is to deploy entirely new instances of the entire application on other resources. However, forcing one module of the application to handle increased load can be unfavorable, leading to an inefficient environment.

Modularity

This principle emphasizes that a microservice should only perform one task and should do it well. Modularity is the concept of different functions being undertaken by different modules, and these modules form the system.

A system consists of isolated components that contribute to the overall system behavior rather than having a single package with full functionality.

Modularity allows each module (analogous to replacing a part of a car) or microservice to be changeable and updatable independently.

This principle can also be considered as the separation of concerns or the functional separation principle.