Microservice Architecture Principles: What They Are and Why They Matter

Over the past few years, microservices have gained popularity as a software development approach. Microservice architectures divide applications into small, autonomous components that communicate using well-defined APIs. This approach has many advantages, including increased flexibility, scalability, and resilience.

Microservice architectures divide applications into small, autonomous components that communicate using well-defined APIs.

This blog post explores the fundamental principles of microservice architecture and how they can be applied to create a reliable and efficient system.

Software applications were traditionally built using a monolithic architecture or a single, autonomous unit. Many developers used this approach until applications became more complex. A monolithic system requires rebuilding, testing, and deploying a new application when modifying a small code section.

In the next generation, microservices were introduced. Microservices involve developing and deploying smaller software units autonomously. The microservices architecture is based on DevOps, which focuses on constantly releasing new features, bug fixes, and security updates. In many cases, it was also used to rewrite legacy applications using modern programming languages.

What are microservices?

Microservices architecture, also known as "microservices," is a method of constructing an application by creating a sequence of independent and self-sufficient services that can be deployed separately. There is a loose coupling between these services; they can be deployed independently and easily maintained. In contrast to monolithic applications, microservices are composed of independent units that contribute to a larger whole.

DevOps is built on microservices since they enable teams to adapt quickly to user requirements through continuous delivery practices.

The microservice represents a single piece of domain logic in a web application. Each microservice provides some functionality for a domain, combining to form an application. To communicate with each other, microservices use APIs like REST or gRPC, but they have to learn how the different services work. The harmony between these microservices is what microservice architecture is all about.

As a result of microservices architecture, developers can organize in smaller teams specializing in different services, with decoupled deployments and other stacks.

For example, Jira is powered by multiple microservices, each providing various features, such as searching, viewing, and commenting on issues.

Typical characteristics of microservices

Microservice architecture has no formal definition, but some common patterns and characteristics are essential.

• Autonomous components

Microservice architectures are built on components, such as software packages, web services or resources, applications, or modules containing associated functions. According to Martin Fowler, "Software components are things that can be replaced and upgraded independently."

Microservice architectures let you develop, deploy, operate, change, and re-deploy components without affecting others.

Components deliver customer experiences or business value in conjunction with other elements. Microservice architectures include a variety of concepts that can be applied to them, including services and libraries, CLI tools, mobile apps, front-end modules, data pipelines, and machine-learning models.

• Clean interfaces

A complex communication mechanism such as RPC, REST over HTTP, or event-driven systems is required once individual components have been established. Microservices may use both synchronous and asynchronous mechanisms. 

An important aspect of microservices is to provide a clear, intuitive contract indicating how a consumer can use them. In most cases, an API is published along with the service.

• You build it, and you run it!

A DevOps philosophy emphasizes the importance of team structures in changing an architecture into microservices. QA, release engineering, and operations are reorganized into one team with one goal: building high-quality products. DevOps methods such as Continuous Integration/Continuous Delivery, automated testing, and feature flags ensure system stability and security. Each team can develop and deploy its own microservices without affecting others. 

It became easier to build, deploy, and run microservices as cloud computing evolved. A number of infrastructure automation techniques aid the teams, including continuous integration, continuous delivery, and automated tests.

The difference between Service-oriented architecture and Microservices

Basically, there are two kinds of web service architectures: SOA (Service-oriented architecture) and microservices. An SOA consists of reusable, specialized components that can be used independently of one another. In both architecture types, service types are classified bureaucratically.

There are four basic types of SOA services:

• Business
• Enterprise
• Application
• Infrastructure services

Underlying services are classified according to their domain-specific responsibilities. 

Microservices, in contrast, have only two types of services: functional and infrastructure.

In both architectures, standards are shared at different layers of an enterprise. The success of an SOA pattern determines the existence of a microservices architecture. Thus, microservices are a subset of SOA. Each service is autonomous at runtime in this case.

Microservices challenges

• A sprawling development process

When you move away from a monolith to microservices, you gain complexity. Multiple teams are creating more services in more places. This makes it difficult to understand how different components relate to each other, who owns which part, and how to avoid negatively impacting dependent components. When sprawl is not managed, development speed will be slowed, and operational performance will be poor. With the growth of a system, it is necessary to have an experienced operations team to handle constant redeployments and architecture changes.

• Lack of clear ownership

There is confusion about who owns what when using a microservices architecture. A DevOps team may deploy an application using APIs, component libraries, monitoring tools, and Docker images. It's crucial to understand information about components, including their owners, resources, and relationships between them. Many teams need to communicate precisely and coordinate to ensure everyone involved can access the required knowledge.

• Exponential infrastructure costs

Testing capabilities, deployment playbooks, hosting infrastructure, monitoring tools, and other costs are associated with each new microservice added to production deployments.

• Added organizational overhead

For microservice architecture teams to coordinate updates and interfaces, there needs to be a higher level of communication and collaboration.

• Testing and debugging

Multi-microservice applications can be difficult to debug since each has its logs. Debugging can become more challenging when a business process is run across multiple machines at different times.

• Emergency response

Having a comprehensive microservice incident response intelligence is vital. The description should tell you who's using the microservice, where and how it's deployed, and who to contact if anything goes wrong.

A perfect match: Microservices and DevOps

DevOps practices are considered integral to their architectures because of the increased complexity and dependencies within microservices. As a result, microservices are considered a foundation of a DevOps culture, which enables:

• Automation
• Improved scalability
• Manageability
• Agility
• Faster delivery and deployment

Key technologies and tools for a microservices architecture

Containers, Docker, and Kubernetes

A container is simply the packaging of an application and all its dependencies, which allows it to be deployed quickly and consistently. Because containers don't have the overhead of their own operating system, they are smaller and lighter-weight than traditional virtual machines. They can spin up and down more quickly, making them a perfect match for the smaller services found within microservices architectures.

With the proliferation of services and containers, orchestrating and managing large groups of containers is essential. Docker is a popular containerization platform and runtime that helps developers build, deploy and run containers. However, running and managing containers at scale is a challenge with Docker alone. Kubernetes and other solutions like Docker Swarm, Mesos, HashiCorp Nomad, and more help to address containerization at scale. 

Containerization and the deployment of containers is a new pattern of distributed infrastructure. Docker and Kubernetes package a service into a container that can be rapidly deployed and discarded. These infrastructure tools are complementary to the microservices architecture. Microservices can be containerized, easily deployed, and managed using a content management system.

API gateways

The individual services in a microservices architecture communicate through well-defined APIs. An API gateway acts as a reverse proxy by accepting API calls, collecting the servicers to fulfill them, and returning results. API gateways provide an abstraction serving a single API endpoint, even though APIs are serviced by multiple microservices. API gateways can also consolidate concerns like rate limiting, monitoring, authentication, authorization, and routing to the appropriate microservice.

Messaging and event streaming

Due to the distributed nature of microservices, teams need a means of sharing state changes and other events. Messaging systems communicate between microservices, allowing some microservices to process events as part of their primary interface. For example, changes to the Confluence page result trigger a reindex for search and notifications to those watching the page.

Logging and monitoring

Microservices make it difficult to identify and resolve an issue across multiple services. Having observability tools for logging, monitoring, and tracing is important. This helps understand how microservices behave, identify potential problems, troubleshoot issues, and debug failures.

Continuous Integration/Continuous Delivery

One of the primary advantages of microservices is frequent and faster release cycles. As a key element of CI/CD, microservices allow teams to experiment with new features and roll back if something doesn't work. This makes it easier to update code and accelerates time to market for new features.

Developer portal

As distributed architectures increase in complexity, development teams can benefit from a tool that consolidates information about engineering output and team collaboration in one place.

Microservice Architecture Principles

Microservices offer many benefits to organizations as the organization and architecture grow and scale. Whether you are refactoring a monolith to engender better cost of scale within your organization, building a new solution from scratch, or just trying to determine if service disaggregation is for you, having principles to guide discussion and development will help.

The principles below are a mix of our original architecture principles (each of which still applies even if not present below), in addition to some new principles dealing with the unique needs of products comprised of services. Many principles also have specific design patterns to help with implementations, and some have anti-patterns to avoid at all costs. The anti-patterns exist to show what types of interactions will violate the principle to the detriment of one or more non-functional requirements like availability, scalability, and cost of either operation or development.

Single Responsibility Principle

In a microservices architecture, the Single Responsibility Principle (SRP) is of utmost importance. It states that each microservice should be dedicated to a special responsibility and should focus on providing a particular business capability. This implies that each service should be self-sufficient and not reliant on other services to execute its function. By adhering to this principle, developers can construct effortless services to test, upkeep, and deploy.

Loose Coupling

A critical principle of microservices architecture is loose coupling. This means that services should be able to operate independently of each other and communicate through clearly defined APIs. In order to achieve this, services should avoid having direct dependencies on other services or shared databases. By minimizing dependencies, developers can create more specific services to test, deploy, and scale.

Decentralized Governance: Empowering Microservices Autonomy

Microservices are unfortunately prefixed with "micro," and many online references suggest they should be tiny and do only one thing. This can be highly misleading without understanding the business value of such a service. A microservice's size is generally evaluated along the dimensions of developer velocity, context, scalability, and availability.

Developer Velocity:

Team velocity is one of the most important benefits of service separation. Team overhead increases as a square of team size when working on a single service between team members. Hence, dividing the code base into separate services to increase velocity can be beneficial, but that requires each service to be owned by an independent team. Having multiple services on one team does not significantly increase velocity. When a team holds too many services, context switching between services and repositories can decrease the rate. The rule of thumb is that each team should possess a different service and should hold no more than three services.

Context:

A context is crucial in identifying components that can be separated, possibly through the development of domains (as in domain-driven design). An ERP system's invoicing context differs from payroll's. There is enough separation between the two to allow them to be within different services, although both are included in the income statement, cash flow statement, and balance sheet. These factors do not suggest they need to be in separate services but rather that they might be good candidates for separation. 

Consider the customer's perspective when setting context-related boundaries for assistance - rather than looking forward from the engineer's perspective. The result of this is that some things should be kept distinct.

Consider the customer's perspective when setting context-related boundaries for assistance - rather than looking forward from the engineer's perspective.

Non-functional requirements in some elements may also need to be paid for and enabled. Payroll, accounts receivable, and invoicing services may deserve a more significant number of instances than reporting services. Separating them from other services may make business sense to make them scalable and highly available. 

As a result, we have the following statements:

• Not everything needs to be small - it doesn't matter that it "does one thing." Doing "one thing" isn't highly correlated with business value. Overly small services, which increase development costs and decrease availability if taken to an extreme, can destroy business value.
• The size and context of services should be constrained.
• Think of contexts and domains from the customer's perspective, not the engineer's.

Service Registry

A Service Registry is used to facilitate communication and discoverability of services. All services are registered with the registry, enabling other services to access the necessary location and information independently. This reduces interdependence between services and promotes independent operation. The service registry also offers advanced features such as load balancing.

API Gateway

In microservices, an API gateway is a crucial entry point for all requests. It takes care of essential tasks such as authentication, routing, and load balancing and can offer additional features like caching, rate limiting, and logging. Using an API gateway enables developers to streamline their system's architecture and establish a unified access point for all requests.

Also, read Quick dive into Microservices: benefits, challenges, real-life examples, and best practices

Continuous Delivery

Continuous delivery is crucial to ensure smooth deployment and management of each service in a microservices architecture. An efficient continuous delivery pipeline guarantees swift deployment of each service with minimal interference to other services. To achieve this, automated testing, deployment, and monitoring tools must be utilized.

Resilience

Microservices must be designed to be resilient, meaning they should be able to handle failures and recover quickly. This can be achieved through redundancy, fault tolerance, and graceful degradation techniques. By designing services to be resilient, developers can ensure that their system remains available and responsive even in the face of failures.

Resilience refers to designing services to be fault-tolerant and able to handle failures gracefully. This includes implementing retries, timeouts, and circuit breakers to handle service communication failures.

Monitoring and Logging

A thorough monitoring and logging system is crucial for maintaining a seamless microservices architecture. This involves monitoring the functionality and accessibility of every service and logging all pertinent events and data. Through diligent monitoring and logging, developers can promptly identify and resolve any problems that may arise, guaranteeing a dependable and steadfast system.

Microservices can cause problems to be identified and resolved across several applications. It is vital for an observability tool for tracking a logger or a tracking device. The software helps to analyze microservices behaviors detect potential problems, and address and fix problems.

Scalability

Microservices should be designed to be scalable, meaning that they can handle increasing loads as demand grows. This can be achieved through horizontal scaling, adding additional service instances to handle the increased load. By designing services to be scalable, developers can ensure that their systems can handle large volumes of traffic without compromising performance or reliability.

Why is Microservice Architecture the Future of Software Development?

Here are some key points to consider:

• The Rise of Cloud Computing: With the rise of cloud computing, businesses are increasingly moving their applications to the cloud, and microservice architecture is well-suited for this environment. Microservices can be deployed on cloud platforms, making it easy to scale applications up or down as needed.
• Increased Agility: Microservice architecture enables businesses to be more agile by allowing them to quickly develop, test, and deploy new services independently. This means that companies can iterate faster and respond more rapidly to changes in the market.
• Better Scalability: Microservice architecture allows for greater scalability by breaking down monolithic applications into smaller, independent services that can be scaled independently. Businesses can easily add more resources to handle increased traffic or demand without impacting the system.
• Improved Fault Tolerance: Microservices are designed to be resilient and fault-tolerant. If one service fails, it does not affect the entire system, and other services can continue to operate normally.
• Easier Maintenance: Microservices can be maintained more efficiently because each service is independent. This allows for more accessible updates, testing, and debugging, reducing the likelihood of system-wide issues.
• Better Team Productivity: Microservice architecture enables teams to work more independently and efficiently, with each team responsible for a specific service. This can lead to increased productivity and faster development cycles.

By adopting microservice architecture, businesses can achieve greater agility, scalability, fault tolerance, maintenance ease, and team productivity, all of which are critical for success in today's fast-paced and constantly changing business environment.

Final thoughts

Microservices architecture is a powerful approach to software development that can help organizations build scalable, flexible, and resilient systems. By following microservices architecture principles, developers can create services that are easy to test, deploy, and maintain and that can adapt to changing business needs. By incorporating automation, monitoring, and logging tools, developers can ensure their system remains stable and reliable, even in the face of failures.

Finally, by ensuring that services are designed with scalability, developers can build systems that can handle increasing loads as demand grows. By embracing these principles, organizations can benefit from the agility and flexibility that microservices architecture offers, enabling them to respond rapidly to changing business requirements and stay ahead of the competition.