6 Fundamental Principles of Microservice Design

Companies must remain proactive and innovative in today’s digital-first environment to keep pace with changing customer demands, emerging technologies, and improved processes. As organizations and their development teams aim to thrive in a continually evolving market, the microservice architecture brings value by laying the foundation to support continuous innovation and the agility to rapidly respond to new demands. 

The evolution of microservice architecture

Before microservices, legacy systems and monolithic architecture weren’t designed to support the rapid development and adoption of new technologies and modern applications. As a result, service-oriented architecture (SOA) was created to speed up project delivery, reduce integration costs, and increase scalability. Unfortunately, while it enabled development teams to make faster connections, traditional SOA introduced complexities and bottlenecks that slowed production times. 

Microservices are the next step in the evolution of SOA, bringing a cohesive, yet granular approach to software development. Its ability to work with multiple components to perform tasks while remaining independent has helped development teams boost productivity.

These capabilities are expressed formally with business-oriented APIs. They encapsulate a core business capability and are assets to the business, further shaping their growing popularity amongst large-scale enterprises. The implementation of the service, which may involve integrations with systems of record, is completely hidden as the interface is defined purely in business terms.

Several intrinsic benefits and business values are derived through microservices, including optimized business functionality, increased scalability, and improved productivity. Positioning services as valuable assets to the business implicitly makes them adaptable for use in multiple contexts. Additionally, the same service can deliver its capabilities to more than one business process or over different business channels or digital touchpoints. 

Microservice design principles

Here are the six fundamental principles of microservice design, each of which we will discuss in more detail below:

1. Autonomy
2. Loose coupling
3. Reuse
4. Fault tolerance
5. Composability
6. Discoverability

1. Autonomy

A key function of microservices is their autonomy and ability to operate independently of each other. Autonomy is a measure of control that the implementation of the service has over its runtime environment and database schema. This enhances the performance and reliability of the service and gives consumers more guarantees about the quality of service they can expect from it. 

Coupled with statelessness, autonomy also contributes to the overall availability and scalability of the service. With increased autonomy, the microservices architecture is less likely to experience failures or performance issues because of another microservice.

2. Loose coupling

Dependencies between services and their consumers are minimized with the application of the principle of loose coupling. By standardizing on contracts as expressed through business-oriented APIs, consumers aren’t impacted by changes in the implementation of the service. 

This enables increased evolvability and new solutions by allowing the service owners to change the implementation and switch out or modify the systems of record or even service compositions that may lie behind the interface and replace them without any downstream impact. Additionally, the increased efficiency and agility in the architecture created by loosely coupled services help to reduce coordination costs and yield faster results, respectively.

3. Reuse

Reuse continues to be a principle of microservice design. However, the scope of reuse has been reduced to specific domains within the business. The effort of designing for this reuse, which in the early days of SOA included wasted efforts in developing enterprise-wide canonical models, was fruitless because it was too ambitious.

However, it’s important to note that the canonical model in its restricted scope can be beneficial. In line with the reuse it facilitates, its scope has been reduced. An emerging model is preferred over a predetermined one with the merit-based reuse approach. Teams can agree on communication models for deciding how microservices must be adapted for use outside the contexts in which they were designed.

A collaboration hub like Anypoint Exchange encourages merit-based reuse with reviews and ratings. If an existing microservice API doesn’t suit your domain or business group, you might be better off building another microservice that does it.

4. Fault tolerance

If a component fails, fault tolerance is the capability that enables a system to continue operating properly. Each service is necessarily fault-tolerant so that failures on the side of its collaborating services will have minimal impact on its own SLA. Services, by virtue of being independent of each other, have the opportunity to cut off communication with a failed service. This technique, called a “circuit breaker” and inspired by the electrical component of the same name, stops individual service failures from propagating through the larger, distributed system.

5. Composability

All the design principles mentioned contribute to the principle of composability which allows the service to deliver value to the business in different contexts. Together with other services to form a new service aggregate, its composition is effectively the new form of application development.

6. Discoverability

Discoverability is to communicate to all interested parties a clear understanding of the business purpose and technical interface of the microservice. Thus, the service must be published in a way that ensures that developers of client software have everything they need to consume it easily.

What’s next for microservices?

As the digital transformation continues and software development relies heavily on continuous integration and innovation, microservices architecture is here to stay. It has many advantages over previous architectural methods, especially in today’s fast-paced world, where solutions that offer increased efficiency, scalability, and innovation bring immense value. 

Many of the world’s largest enterprises continue to shift from a monolithic approach to implementing microservices. However, it’s important to be aware that this architecture can create disorganization and lack of governance if not managed properly.

Microservices require more complex coordination and a systematic approach to implementation. Products developed with a microservices architecture will also need to be integrated with legacy technology stacks. If this is done poorly, it can create technical debt and more operational costs for the IT team. 

Therefore, instituting microservices to create a competitive advantage, improve software quality, and help your company innovate faster goes beyond a mere selection of products and software. Enterprises can better govern and manage their services by integrating a service mesh, an architectural pattern for microservices deployment, into their microservices strategy as it helps companies scale, maintain flexibility across services, and accelerate microservice adoption.