How Microservices Architecture Works 

Microservices architecture is a flexible, scalable, and modular style of developing software applications. It involves splitting large applications into small independent parts that perform specific functions. 

Generally, the architecture provides a framework to create, update, test, deploy, and maintain each service independently. As such, it allows developers to build applications as a collection of several autonomous services. 

Most modern cloud-native applications are good examples of microservices built using containers. The containers comprise a set of all the codes, libraries, executables, files, and other resources that a microservices requires to run. Consequently, developers can build applications without worrying about dependencies. 

Today, companies such as Netflix, Amazon, Uber, eBay, and others have shifted from traditional monolithic applications to microservices. The change has resulted in more customer-friendly applications and reliable and improved services. 

Overview

As businesses continue to look for ways to remain competitive in an uncertain and complex environment, they are looking for ways to improve efficiencies. In particular, software developers are adopting new methods to build and maintain applications, add features, and more. 

Towards this, they are shifting from the monolithic to the microservices architecture. And this allows them to build applications and new features faster and reliably. Also, developers and businesses can update applications regularly using smaller, cross-functional, and loosely coupled teams. 

The microservices architecture supports continuous development and deployment of software. Each team can build a series of small changes and test the application and new features faster using an automated deployment pipeline.  

Ideally, the architecture overcomes most of the challenges and limitations of monolithic architecture. By breaking down the large and complex applications into smaller units, it makes it easier to develop large and complex applications as a collection of multiple independent sub-units. 

How Does the Microservices Architecture Work

Microservices architecture is a style that allows developers to build an application as a collection of loosely coupled, independently deployable services. Each service, owned by a small specialized team, is self-contained and focuses on addressing a specific business function. 

Teams can build, deploy, modify, test, and maintain each of the units independently without affecting the other services. Unlike a monolithic application where all services are bundled into one unit without any boundaries, the microservices architecture splits every business functionality into a single independent unit.

Each microservices focuses on a particular function, such as logging, invoicing, searching, messaging, etc. Combining the multiple microservices results in a single application with different features. While some microservices can perform a certain business function individually, there are times when two or more services work together to do a larger complex task. 

In the architecture, developers may break down a large complex application based on the business or functional requirements (vertically). This results in smaller independently deployable subunits. 

Some operations require only a single microservices. However, some complex or demanding operations are distributed across several microservices. In such a case, the subunits communicate with each other using lightweight synchronous or asynchronous, language-agnostic network calls, such as REST, gRPC, or messaging.

Additionally, clients do not talk to the microservices directly. Instead, they use API gateways that forward the request to the appropriate microservice.

Characteristics of a Microservice Architecture

Each microservice or application process operates as a loosely coupled, separate service with its logic and dependencies. And teams can modify, test, update, deploy, and scale the microservice without affecting the others within the same application.

Some characteristics of a microservices architecture are:

• The application contains several separate independently deployable processes. However, the system may call multiple microservices to serve a single user request.
• The architecture supports granular and horizontal scaling.
• The microservices have external boundaries and do not communicate internally with each other. Instead, they talk to each other via lightweight network calls such as RPC and messaging.
• It comprises specialized and simple units, each of which addresses a specific business function or issue. Most often, each development team has expertise in a particular component.
• As demand for more functionalities increases, developers may add more code which will make the application more complex. In such a case, teams can further break it down into more independent and easier-to-manage services.

Monolithic Vs. Microservices Architectures

In a monolithic architecture, if demand for one feature spikes, the developers must scale the entire architecture. Adding new features or modifying an existing application is complex, time-consuming, and costly.

Also, the impact of a failure in one component may affect the availability of the entire application, especially when the components or processes are dependent on each other.

Some of the main disadvantages of a monolithic application include:

• Low reliability since if a single component fails, the entire application will not work
• Not easily flexible 
• Difficult to scale 
• Slow development since a feature must be built first before moving to the next step
• Not suitable for large and complex applications due to its inflexibility and slow development

In a microservices architecture, different and independent components are used to build the application. Each feature or microservice runs as an independent service, and when there is a need to add or modify features, you do not need to upgrade the entire architecture. Instead, you only build the required components.

This allows you to update, deploy or scale or run each service independently based on your business needs. Additionally, the impact of a failure in one component is smaller as compared to a monolithic application where everything goes down.

Benefits of Microservices Architecture

The major benefits of a microservices architecture are:

#1. Easy and Flexible Scaling of Services

The microservices architecture enables developers to scale each service independently to meet unique demands for the specific feature.

With this, the teams do not have to scale the entire application. Instead, they only focus on the unit which has a higher demand and consequently scale it together with its associated infrastructure.

#2. Better Resilience

Since the microservices are independent and self-contained, a problem with one service will only degrade the application and does not result in a total failure. The other good microservices will continue operating, and only the affected feature will be unavailable.

In a monolithic architecture, a problem in one feature is likely to cause the failure of the entire application. 

#3. Reusable Code

Developers can use some modules to perform multiple processes. For example, a microservice performing a certain task may also work as a building block for another service.

As such, the developers can build additional features without writing new code from scratch. Instead, they can re-use part of the code for another service.

Other benefits are:

• The microservices architecture takes advantage of containers, serverless computing, DevOps, and other modern software development technologies.
• It allows developers to create and deliver several services concurrently.
• Ability to test, troubleshoot, update, or remove certain functions without affecting others.
• Shorter development cycles and faster deployment.
• Smaller development teams

Disadvantages of the Microservices Architecture

Microservice architecture provides benefits such as enabling fast, frequent, and reliable development of large and complex applications. However, it also has some drawbacks and limitations.

• For large applications, there could be complex coding challenges between the microservices. 
• Managing security is a challenge as the number of microservices increases and the application grows. In practice, the architecture results in a widely distributed system with a larger attack surface, complex access rules, and more network traffic to monitor. For example, there are many exposed ports, APIs, and other components, such that traditional security tools and firewalls cannot secure adequately. This makes the microservices vulnerable to DDoS, man-in-the-middle, cross-site scripting, and other attacks.
• Troubleshooting large and complex applications becomes more difficult as they grow. A large number of modules communicating with each other may result in communication overhead due to increased network traffic and RPC calls. 
• A large number of services, processes, containers, databases, and other moving parts bring in the complexities and challenges of a distributed system. 
• As applications grow larger and more complex, ensuring transaction security is difficult. 

Microservices Architecture Tools

Microservices architecture enables smaller teams to develop individual loosely coupled services. To remain competitive, the teams need to use various tools to support the framework, automate some repetitive tasks and speed up the deployment of apps and new features. 

The microservices tools differ in capabilities and other features. As such, the choice depends on the specific needs and what the developers want to achieve. 

 Some common tools include:

1. Operating systems such as Linux and Windows
2. Programming Languages – Spring Boot, Elixir, Java, Golang, Python, Node JS
3. API management and test tools API Fortress, Postman, Tyk 
4. Messaging tools – RabbitMQ, Amazon Simple Queue Service (SQS), Apache Kafka, Google Cloud Pub/Sub
5. Toolkits – Seneca, fabric8, Google Cloud Functions
6. Architectural frameworks – Kong, Goa, Helidon, Quarkus, Molecular
7. Orchestration tools – Conductor, Kurbenetes, Azure Kurbenetes service (AKS), Apache Mesos, Amazon Elastic Container Service.
8. Monitoring tools – Logstash, Graylog Elastic Stack, Middleware
9. Serverless tools – Kubeless, Claudia, Apache Openwhisk

Microservices Architecture Use Cases

Microservices are ideal for various industries and applications where they improve performance and efficiency. Below are some of the common use cases:

#1. Data Streaming 

When there is a need to stream and process large amounts of data from single or multiple sources, microservices can help to improve efficiency and performance.

#2. Scalable Web Applications

Although some web applications are usually monolithic, using the microservices architecture can improve scalability and performance. 

#3. Internet of Things (IoT) Applications

IoT application developers can use the microservices architecture to build the applications. This allows them to build small, lightweight, independently deployable, and manageable applications.

#4. Extract, Transform, Load (ETL)

ETL is s technology that extracts data from single or several sources, transforms it into the desired format, and loads it into another data store or database. The microservices can help to improve the scalability and performance of such ETL processes.

Examples of Companies Using the Microservices Architecture

Some of the major technology companies that have embraced microservices include;

Amazon

Amazon is one of the major promoters of microservices architecture. As the company and customer base grew, the monolithic application they had became unstable and unreliable.

To address this, they moved to the microservices, which now ensure easier maintenance, adding of new features, and maintenance of individual independent services, hence preventing complete outages.

Besides using microservices on the Amazon shopping website, they also offer an infrastructure, the Amazon Web Services (AWS), where businesses can build, host, and manage the microservices. 

Uber

Initially, Uber relied on a monolithic application that was adequate for a city where it was offering services. However, as the company entered new markets and regions, the application could not support the users efficiently.

To ensure reliable services, Uber shifted to the microservices-based architecture for certain features such as travel management, passage management, etc.

Netflix

With microservices, Netflix has managed to overcome the scalability challenges it was experiencing as the customer base grew.

It uses over 500 cloud-based microservices to process about 2 billion requests daily. Besides improving reliability and availability, the microservices architecture has reduced the cost of streaming.

Final Words

The microservices architecture provides several benefits compared to the monolithic systems. These include faster deployment of applications and features, high flexibility and scalability, resilience, and more.

However, it also has some drawbacks and may not be suitable for all applications. For example, it may not be cost-effective for smaller applications. 

Additionally, as the applications grow in size and features, it is more difficult and costly to build, deploy, and test the subunits, especially if distributed across different clouds and network environments.

As such, it is vital to evaluate and understand the benefits and cons of the microservices architecture before adopting the technology.

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