What are Microservices—an Introduction to Microservices Architecture

Microservices, also referred to as microservices architecture, is a modern software design technique that is promising to redefine the building of enterprise applications.

With the rapid advancements in technology and ever-evolving consumer needs, traditional development methods are unable to keep up the pace.

However, microservices architecture allow enterprises to swiftly, reliably, and frequently deploy huge, complex applications, which enhance innovation and accelerate time-to-market.

In this article, we’ll talk about microservices architecture and how this cutting-edge development style can help you to take your applications to the next level.

Let’s get going…

What is Microservices Architecture?

Microservices is a growing architectural style that aims to build a single application as a suite of small, loosely coupled services or components, each performing its own tasks and communicating with one another via light-weight mechanisms, usually an API HTTP resource.

Although these services are deployed independently, they work together to provide a seamless and responsive performance.

If you’re developing an application using this technique, you’ll separate it into different functionalities and create each as single-function modules with well-defined roles.

In other words, the application is simply the combination of its constituent parts. The term “micro” in microservices suggests that these are small applications combined together.

For example, let’s say you’re using the microservices technique to develop an e-commerce application. In this case, you’ll deploy the different features of the application—such as search, payment, and customer reviews—in separate, independent codebases, instead of stuffing them in a single repository. In the application, every microservice will represent a single business capability.

Here is a diagram that illustrates the microservice architecture of the e-commerce application:

Microservices vs. Monolithic Architecture

To understand microservices better, let’s compare them with the technique used before their development—monolithic architecture. With monolithic applications, all the software components are tightly coupled and deployed as a single instance.

Monoliths contain all the functions in one structure; all the processes interact with the same server and are ultimately run on the same machine.

In other words, while microservices aim to separate applications into smaller parts, monolithic architecture develops applications in a single piece.

Here is a diagram that illustrates the design of the e-commerce application mentioned above using the monolithic approach:

This kind of architecture can lead to some benefits, especially because it allows for the cross-cutting of concerns, such as search features, audit trails, and security capabilities.

Since everything is operating within the same application, it’s a simple way to deploy and ensure that the components are connected to those cross-cutting concerns.

Furthermore, it can make applications perform faster because all the processes are coalesced as one piece without involving communication with external APIs.

However, with the expansion of web technologies and the increasing consumers’ needs for agile and robust applications, the monolithic approach has several challenges that make it difficult to keep pace with these changing demands.

Since the monolithic approach relies on tightly coupling all processes, if one process experiences any anomaly, it could potentially jeopardize the well-being of the entire application.

Furthermore, as the requirements of the monolithic application grow, it becomes difficult to isolate services for independent scaling, maintaining the code, or implementing any new ideas.

Therefore, this traditional architecture cannot meet the demands of the new technological age, where constant adaptation and innovation is desired. The above challenges are the main reasons for the rapid evolution of microservices.

Here is an image sourced from Martin Fowler’s blog (who is a renowned software developer and author) that illustrates the differences between monoliths and microservices:

Microservice vs. Service Oriented Architecture

Both microservices and Service Oriented Architecture (SOA) are usually regarded as service-based architectures, implying that they allow applications to be created as a suite of small, de-coupled services, which are operating in their own environments and are deployed independently.

Technically, it can be said that microservices evolved from SOA—it’s the implementation of SOA principles.

In spite of their similarities, the two architectures have subtle differences, especially in how the services are deployed as well as the size of modules. While SOA applications follow the “share-as-much-as-possible” architectural design principle, microservice applications follow the “share-as-little-as-possible” principle.

In microservices, the services or components are usually fine-grained, and the protocols light-weight. On the other hand, SOA utilizes larger, more coarse-grained modular services.

Also, while microservices communication occurs through a simple API layer, SOA communication occurs through an Enterprise Service Bus (ESB).

In SOA, individual components, each focused on achieving a specific business objective, follow a communication protocol, such as ActiveMQ or SOAP, for sharing themselves within the ESB.

Moreover, microservices usually offer quick and easy deployment and scaling options, while SOA offers less flexible deployment and scaling options.

Here is an image sourced from Kanban Solutions blog that illustrates the differences between monolithic, SOA, and microservice applications:

In recent years, these differences have made the microservices architecture to be lauded as a revolutionary game-changer, while SOA’s dominance has been increasingly diminishing.

Microservices vs. APIs

Probably, you may be asking yourself: is an API a microservice? To answer that question, let’s talk about the differences between microservices and APIs.

Generally, Application Programming Interfaces (APIs) refer to a set of programming instructions that allow computer systems to “talk” to one another and share functionalities. An API exposes an application’s data, allowing developers to fetch its features and build powerful integrations.

There are APIs for almost anything you can think of. For example, you can use a payment API to build an application for sending and receiving payments, a weather API to include weather predictions on your application, or a retail API to add shopping capabilities to your application.

Let’s refer to the earlier example of building an e-commerce application using the microservices technique. In such a situation, you’ll have three services: the search service, payment service, and a reviews service.

So, for these services to communicate with one another and complete the client’s request, they’ll need APIs. Every microservice will have its own API for interacting with other services within the application.

While microservices is an architectural style that allows applications to be created as small, autonomous services, APIs are what facilitate the communication between the isolated pieces of software within a microservice application.

An API can actually be viewed as a part of a microservice architecture, allowing communication between its various components.

Worth mentioning, with the current evolution of APIs, most microservices are defined using REST APIs, which have become more dominant than SOAP APIs. So, today’s REST APIs play a critical role in developing loosely coupled microservices.

Importantly, APIs are not always exclusively used with microservices. APIs are used whenever two software systems are needed to talk with one another—which may not involve microservices.

Advantages of microservice architecture

Robert C. Martin, a renowned American software engineer and instructor, devised the single-responsibility principle, which states that “gather together those things that change for the same reason, and separate those things that change for different reasons.”

Microservices implement this principle by decomposing an application into various smaller, independent services. Consequently, this leads to several microservices architecture benefits, including the following:

1. Agility

Since the microservices architecture focuses on modularity, wherein each service operates independently, it is easier to manage different types of changes during the development process.

If you want to fix a bug, update a service, or make any improvement, you can do so without the need to redeploy the entire application.

In most traditional monolithic architectures, if a bug is discovered in one section of the application, it can hamper the entire release process.

With microservices, enterprises can confidently modify existing features or add new ones without bringing the application to its knees.

Moreover, isolating faults in microservices is possible. If a single microservice fails, the rest of the application will continue to work—unlike in monolithic systems.

2. Enhanced team productivity

Microservices allow for small, focused teams that are organized around business capabilities. Each unit is responsible for building and operating a specific feature, leading to increased flexibility, autonomy, and, importantly, a faster development cycle.

Large teams are usually less productive because of difficulties in management, communication breakdowns, and poor motivation.

In a study that investigated how team size affects teamwork in software development projects, it was found out that teams of three members achieved a quality score of 63% while teams of nine members achieved 28%.

With microservices, onboarding new developers into teams is much faster—as it’s easier to understand the code in small, distributed services than a whole monolithic application.

Additionally, the microservices architecture gives teams the technological freedom to select the best technologies and tools for solving their specific problems—instead of being limited to a one-size-fits-all approach.

This way, teams can make use of the latest technologies, mix various technologies, or concoct the best technique that fits their service.

Furthermore, this architectural style enables teams to use functionality modules for multiple purposes.

For example, a service built for a certain function can be reused in developing another feature without writing its code from scratch.

This ability to reuse already developed capabilities can save the resources of an enterprise and allow teams to have more time to focus on their core tasks.

3. Enhanced scalability

Microservices are greatly beneficial for scaling. Since the functionalities are deployed independently, you can monitor and scale them separately without harming the entire application.

If the demand for certain services grows, it is easier to right-size infrastructural needs and make improvements to cope with the spike.

The possibility of isolating features and scaling them independent of the rest of the application makes microservices ideal for creating modern, complex systems.

Microservice Architecture Challenges

Unfortunately, the microservices software development style is not a silver bullet. It comes with several drawbacks that you need to address before you can make the most of it.

Here are some microservices architecture disadvantages:

1. Complexity

As compared to an equivalent monolithic application, a microservices application comes with significantly more moving parts.

Although the individual services (components) may be simpler and easier to manage, as a whole, the entire application ends up being complex.

The structure of a microservices application can also complicate development and testing. The approach for developing a single component (that depends on other components within the application) may not be as straightforward as developing a normal monolithic application.

Moreover, most existing development tools are not suited to work with components that have several interconnections.

As such, refactoring across component boundaries may be complicated to realize. Furthermore, it becomes challenging to test those interdependencies, particularly if the application is growing rapidly.

Therefore, because microservices are highly distributed software systems, your team needs to have the right expertise to implement them successfully.

2. Difficulties in governance

Although the decentralized methodology used in microservices architecture is beneficial, it can complicate governance.

As the number of services increase, different technologies get entrenched, and third-party resources get integrated, gaining visibility and managing the whole application may be difficult.

Therefore, to succeed with microservices, you need to set up a centralized monitoring and logging system that allows you to bring everything together and identify sources of problems easily. This way, coordinating the different teams becomes easy.

With such a system, you can pinpoint issues early enough and significantly overcome the difficulties in governing microservices.

3. Higher operational overheads

Implementing microservices architecture can also be more costly. Since the services are deployed on different servers, the application may need several runtime environments and CPUs.

Moreover, microservices usually make numerous remote calls, as the interdependent services need to communicate with each other frequently. Consequently, these factors, and others, lead to higher operational overheads.

Furthermore, the increased security requirements of microservices also expand their development budget. The decentralized approach of the microservices architecture exposes more “soft targets” for attacks.

Therefore, safeguarding a microservice from malicious intrusions needs to be prioritized.

Examples of Microservices

Since their emergence, microservices have been gaining popularity rapidly. In fact, according to the findings of the 2018 Global Microservices Trends report, which interviewed 353 development professionals, 91% of the respondents are using or are planning to implement microservices.

Because of the benefits of the microservices architecture style, most applications that were initially designed as monoliths are now evolving towards the microservices direction.

Here are some examples of popular applications that are spearheading this new development style:

• Amazon, which is the largest e-commerce company in the world, had its retail website as a gigantic architectural monolith in 2001. To scale its services and deploy changes quickly, they broke their applications into small, independently-deployable, and service-specific components. So, Amazon was using the concepts of microservices even before the term had been invented. Consequently, what began as a clean-up of Amazon’s systems ended up pioneering what we now know as microservices. More so, this made Amazon create several solutions that enhance the adoption of microservices, such as the widely popular Amazon Web Services (AWS). Without moving to microservices, Amazon may not have grown to its current status.

• Netflix, which is a widely used video streaming service that accounts for about 15% of all Internet traffic worldwide, ushered a revolution in around 2010 by moving from a monolithic to a microservices architecture. The company is one of the first implementers of microservices. Just like Amazon’s story, when Netflix started rewriting the applications that run their entire video streaming service, the “microservices” term had not even been coined. Today, the service is driven by a robust and expansive architecture that involves over 500 microservices making over two billion API requests per day.

• Other companies that are using the microservice architecture include eBay, Coca Cola, Etsy, Spotify, and many others.

Conclusion

Although not a panacea, the microservices architecture promises to supercharge the capabilities of your applications through distributed development.

It’s suited for building complex, multi-functional applications that can meet the current demands for agile and user-centered applications.

Importantly, before going for the microservices architecture, you should carefully evaluate your needs and abilities to meet the requirements of this innovative software architectural style.

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