SOA vs. Microservices: A Head-to-Head Comparison

Kumar Harsh  on January 19, 2022

Traditionally, monolithic architecture has been used to develop large-scale apps. However, people have realized its drawbacks and limitations over time. Without adapting to modern agile practices and limited flexibility does not allow for a productive development process. Therefore, organizations have been searching for better, more reliable architecture to facilitate the development of large-scale, complex apps with a more productive workflow.

From the pile of architecture designs, two alternatives appear to top the charts—service-oriented architecture and microservices. At a glance, these two designs seem pretty similar. In fact, they are quite similar in some ways. Both of these architectures involve cloud environments and support agile development. They can scale quickly to meet large apps’ speed and operational requirements. And fundamentally, both of these use the same concept—breaking down large apps into smaller, more flexible components.

Owing to all these similarities, it can sometimes become difficult to distinguish between the two. This is why we have put together this guide. This article will walk you through the differences between SOA and Microservices architecture and suggest situations suitable for using either of them.

Overview of Key Differences Between SOA and Microservices

Here is a quick table to summarize the key differences between the SOA vs. Microservices.

Service-Oriented Architecture

Microservices Architecture

Maximizes application service reusability

Focuses on decoupling

Systematic changes require modifying the complete monolith

Systematic changes are generally done to introduce new features

DevOps and CI/CD are not mainstream

Strong focus on DevOps and CI/CD

Focuses on reusing business functionality

Focuses more on bounded contexts

Uses Enterprise Service Bus as an interface for enterprise apps

Uses a less elaborate, more straightforward messaging system as an interface

Supports multiple message protocols

Uses lightweight protocols such as HTTP, REST, or Thrift APIs

Uses a common platform for deploying all component services

Standard app servers are not used; utilizes cloud technologies for more efficient deployment

Containerization is not very popular

Utilizes containerization well

Shares data storage across business components

Each microservice component can have its own data storage

Common governance and standards

Relaxed governance, with more focus on collaboration and freedom of choice

Structurally, this is how the two architectures vary. They are mainly similar to each other because the lowest-level services and APIs in microservices are more loosely coupled than the SOA architecture.

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What is Service-Oriented Architecture?

Service-Oriented Architecture is an approach for building software that incorporates complete enterprise development. SOA enables development teams to reuse components from other pre-existing applications across the entire enterprise. SOA promotes the development of a collection of modular services and can communicate with each other to support a system of applications.

This architecture enables communication between various platforms and languages. SOA bases its structure on decreasing the coupling between application components, also known as loose coupling or decoupling. So two components can easily communicate with each other even if they are entirely different. This improves business functionality and makes software development more convenient.

SOA offers four different kinds of services. These are:

How SOA Is Structured

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Source: O’Reilly

Service-oriented architecture is one of the industry’s most standard and easy-to-use design methodologies. You create high-level services in your application based on their business objectives. In the above example, a bookstore application has been implemented using service-oriented architecture. Four crucial, distinct segments of such an app are:

The service-oriented architecture suggests that each segment should have its own services (i.e., components that manage their functions). This is why four services are built in the providers’ layer. All of these are connected to a pool of databases that store all application-related data. This is where coupling comes in; services can not be tested or modified independently because they share their datastores.

An interface (the Enterprise Service Bus), in this case, unifies all services together and exposes APIs for the frontend clients to communicate with the Providers layer. The Consumers Layer can have any kind of application that can interact with the SOA interface. You can reuse the same Providers Layer for a variety of frontend clients and endpoints.

Advantages of Service-Oriented Architecture

Now that you know how service-oriented architecture works and manages things internally, it is vital to understand its effects on your business. Here are some of the best benefits that SoA offers to your app & business.

Faster Time to Market

Service-oriented architecture relies heavily on reusability. It helps you to assemble working applications from more minor, reusable services rather than rewriting and reintegrating new services for each new project. This enables development teams to build apps much faster and adapt to changing business requirements swiftly. 

A service-oriented approach to application development supports scenarios for inter-application integration, data integration, and service orchestration automation for business processes and workflows. This enhances software design and development speed by significantly decreasing the time spent in rebuilding and increasing the time spent on delivering and improving the applications.

Ability to Leverage Legacy Functionality in New Markets

Well-designed and built service-oriented applications enable developers to extend functionalities from one environment to another without being locked down by the computing platform or environment. 

For instance, many companies use a service-oriented architecture to expose services and functionality from mainframe-based financial computing systems to modern client-based web applications. This enables their customers to serve themselves directly with financial information and processes accessible only via company employees earlier.

Improved Collaboration Between Business and IT

Service-Oriented Architecture promotes the collaboration and synchronization between business and IT teams by distributing services based on business terms. This way, each service has a business purpose and can be evaluated accordingly based on its performance, health, etc.

Defining services based on business terms also enables business analysts to work more efficiently with developers on all insights mentioned above. This will further lead to better results.

Loose Coupling and Platform Independence

Service-Oriented Architecture supports the creation of complex applications by combining together services generated from entirely independent sources and coupling them loosely on the application platform. This gives your app the ability to run and develop without depending solely on a limited set of platforms and technologies.

In the object-oriented design paradigm, coupling or interdependence between various classes is discouraged to foster an environment where code modules can be changed or removed without breaking the application’s functionality. SOA promotes this practice by enabling the development of independent services that enhance the efficiency of the software and the development process.

Enhanced Agility

The ability to construct applications by piecing together reusable components and services promotes agility in the development team. As a business owner, you get the ability to quickly come up with variants and derivatives of your product based on changing requirements. 

Unlike traditional development, you do not need to start development from scratch if you need to remove one deep-rooted feature from your app. There are no “deep-rooted” features anymore; everything is a service and can be removed or modified using the same amount of effort.

Easy Maintenance

Since the application has well-defined constituents and can be easily separated and put back together, maintenance becomes an easy job. You do not need to worry about all the other functionalities while testing and polishing a particular feature (i.e., service). In traditional monoliths, this was rarely possible. You had to run extensive integration tests to check the intricacies of a smaller segment or module hidden somewhere deep in code. Updating the module was another pesky job; you had to ensure not to break any other module in the process. SOAs get rid of these complications once and for all.

Parallel Development

One of the coolest and most practical advantages that SOAs offer is the ability to build a project parallelly. In traditional monoliths, development was often forced to be sequential since most features were interdependent. SOA removes this constraint by isolating features in the form of services based on their purpose. Now since these services function independently of each other, they can also be developed independently. You can have various teams working on one service each and delivering the complete application much faster than creating a traditional monolith.

Promotes Interaction

While we mentioned service-oriented architecture-based apps could be platform-independent, they are better when they are platform-independent. Not all types of apps or services perform equally across all platforms and runtime environments. Some services suit certain technologies better. To leverage this feature and build a highly optimized ecosystem, you should use various technologies and runtime environments to develop your services. You can then unify them together via a central interface. The service-oriented architecture enables you to do this.

Potential Disadvantages of SOA

While the list above might seem quite compelling and descriptive, there are some other factors to consider before adopting service-oriented architecture. There are a couple of disadvantages and limitations of this architecture which we will discuss in this section.

Extra Overload & Increased Response Time

Since a service-oriented application splits an extensive, well-woven application into multiple independent services, it can often increase the processing capacity required for running the application. Each module of the older monolith application is now a standalone service with its lifecycle processes. This is not suitable in cases where you have a limited budget and resources.

Also, since each functionality rests behind its service now, inter-service communication is a significant factor in determining your application’s overall throughput. And no matter how efficient the inter-service communication is, the overall response time of the app will be increased compared to a monolith due to the mere presence of inter-service communication.

Large Upfront Cost

Since service-oriented architecture involves extensive planning and intricate design of the application well before development begins. Furthermore, the development process of SOAs is different from that of monoliths, as each service needs to be made fully self-reliable. This further adds to the cost of development.

Also, SOAs require additional technologies to unify the variety of services together under one hood. The hosting and distribution of such applications vary from that of the traditional monoliths. All these factors contribute to an increase in the overall cost associated with the development of SOA-based apps. However, it is essential to say that the cost to value ratio in SOAs is excellent, and you get good value for all of the money and resources you invest into it.

High Bandwidth Server

As already mentioned above, SOA-based apps rely heavily on inter-service communication. This requires the apps to send and receive millions of requests per day, based on user traffic. To enable this, the app servers need to handle high bandwidth and serve content at high speeds. This adds to the cost of the setup and can be a little challenging to maintain uniformly throughout.

Complex Management Due to Vast Variety of Services

Since SOA is composed of various services, managing the app, in general, can be a complex task. You need dedicated teams for each service specialized in the service’s stack and a high-level team that is skilled adequately in all stacks to overlook the entire application. Finding and training such resources can be tough, let alone updating them whenever the technology changes. Therefore, you should be ready for a complex management process when adopting service-oriented architecture.

What are Microservices?

In a nutshell, microservices are an extension of service-oriented architecture. The various components of microservices communicate with each other via APIs. Each microservice is focused around a specific business domain and forms an organizational network for it. These components are used together to create complex applications and high-level services. Microservices architecture crafts an application’s system in the form of single-purpose units of services that are usually unique from one another.

When implementing microservices, developers can update the codebase with ease. This architecture also makes scaling very easy and independent of other code components. You can easily choose varying tech stacks for various components and connect them all together using APIs. Load balancing and fault tolerance are quite high with microservices since each component is distinct and manages itself independently. Microservices-based apps are usually hosted on the cloud to gain cost and efficiency advantages.

How Microservices Architecture Is Structured

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Source: Microservices.io

Microservices structure is quite self-explanatory and straightforward. You break down your application in terms of business objectives and functions. In the above example, an e-commerce application has been implemented using microservices. Three essential and distinct features of such an app are:

The microservices architecture dictates that you should provide these functions with independent components of their own. As you can see, three components are built for these features, and each of them is connected with its own independent data stores. This is a crucial trait of a microservices-based system—all resources must be independent, discreet, and as loosely coupled as possible. If the need to access two resources at one point arises, usually its corresponding service exposes a method to do so.

A front-end web interface then accesses these services to allow users to interact with the application. The same services are reused to integrate with another front-end app for mobile devices. In this way, the app is structured on business concepts, and code reusability is maximized.

Advantages of Microservices Architecture

Moving on to microservices, they offer an extended range of benefits over traditional monoliths and SOA alike. This is probably why they are more prevalent in the modern software industry than other architectures. Here are a few benefits of using the microservices architecture.

Small Modules

One of the most significant benefits of employing microservices in your app is the extensive modularity that they offer. With service-oriented architecture, you can break your sizeable monolithic application down into smaller services based on the purpose that they fulfill. But with microservices, you can break down these services into smaller, singular microservices that perform a smaller yet integral subtask of the service's tasks.

Modularisation inside services helps reuse the service's components to build other similar services quickly. It is like an extended version of service-oriented architecture; you start with a handful of microservices to build up some significant services and then use these high-level services to build an application. 

Easier Process Adoption

Since we are talking about an even lower level of organization with microservices, adopting new technology and processes becomes much easier. You can have a small number of microservices running on JavaScript while others use the Java runtime to complete heavy tasks. If you need to bring in Go or Python into your project somewhere down the line for their extensive collection of third-party libraries and community support, you can easily do so. Microservices give you unmatched freedom in terms of technology and software process adoption.

Independent Scaling

Scaling is another region where microservices outshines its competitors. Due to its discrete structure, scaling individual components based on traffic and other requirements is easy. In most situations, it is highly efficient, too, since there are usually distinct regions in an app that receive more traffic than others.

With the microservices architecture, you can scale each module independently via x-axis scaling (cloning with more CPU or memory) or z-axis scaling (sharding).

Independent Operations

Similar to service-based architecture, microservices are independent of each other, and thus you can modify/add/remove a microservice without affecting any other microservices in your application. You can have multiple teams working on individual microservices without worrying about breaking the app’s functionality. This gives your team both a speed and a productivity boost.

Fast Time to Market

One of the useful benefits of implementing microservices in your application is to hit the market faster than usual. Since you put in a lot of effort in planning and designing your app well, you know which microservices you can reuse multiple times to reduce code size. With such planning, you can get your app running very quickly by building the essential microservices first and piecing them together to create your app. Over time, you can make more and more microservices to add new features to your app gradually.

Easier DevOps

DevOps is one of the most integral components of software development cycles today. More and more teams are looking to simplify their DevOps processes to spend more time building features and less on deploying and distributing them to end-users. Microservices help you do just that by splitting your application into small, identical, independent entities that you can deploy uniformly. You can add most microservices to a new DevOps process with a few clicks. Automating routine procedures such as scaling is an effortless task.

Increased Fault Tolerance

Increasing fault tolerance is another significant benefit of splitting your app into smaller microservices. If your app provides three simple features to its end users and you have three microservices, your app will still keep functioning and provide two features properly if one of the three goes down. This would not have been possible in a monolithic situation since a fault would have taken down the complete application and restricted user access to even those sections that were just fine.

Potential Disadvantages of Microservices Architecture

Even though microservices architecture sounds like it is the best way to design modern apps, it has its limitations and disadvantages to use-cases. This section will discuss some of the possible ways microservices might affect your product’s growth or performance.

Complex to Monitor and Debug

After moving past the configuration difficulties, you will stumble into the uncertainties of monitoring and debugging. One of the biggest benefits of using a monolithic structure for your app is that everything stays under one hood and can be monitored in one place too. Even with service-oriented architecture, a layer unifies all services and can help in monitoring. But with microservices, everything is discrete and independent. More often than not, developers end up employing custom and irregular methods of monitoring and debugging, which causes issues later down the road.

Distributed tracing, centralized logging, dashboards, etc., are possible ways to solve this problem. However, none of them are sure to work in every case; you need to explore and find out which works best for you.

Automation

Since a microservices architecture houses a large number of smaller components, you need to look into automation to carry out all routine tasks. It is simply impossible to build, deploy, and monitor each component manually when there is a change. Therefore your automation game needs to be up to a point to handle the workload.

Mishaps in automation can cascade down the hierarchy of microservice components very quickly. Therefore, you need to be careful while defining automation scripts and thoroughly test each of them.

End-to-End Testing

Testing is another region of software development that depends on the modularity of code. While increased modularity promotes and makes it easy to unit test the code, testing the modules together in action becomes tough. The possibility of using varying runtimes for each component presents varying performance standards for the system. Also, all of a workflow’s dependent services need to be up and running to test that workflow.

Sensitive Security Measures

Since a high amount of network communication is involved, there is an increased risk of security breaches in the exchanges. On the other hand, monoliths are mostly aloof from this issue since there is little to no network exchange between app components. Therefore, when you opt for microservices, you should prepare well on the security front and ensure that none of your super-sensitive user data leaks out because your networks were not secure enough or the shared infrastructure you were using did not isolate its customers’ activities properly.

Choosing Between SOA and Microservices

An app can be designed using both service-oriented and microservices-based architecture. Therefore it is essential to know when to use each of these architectures. This section will help you with that.

When to Choose Service-Oriented Architecture

Here are some cases in which you should opt for service-oriented architecture.

To Develop Independent Services

If you are looking to develop multiple independent services, SOA is probably a better choice. There are no dependencies involved in such a case, and an SOA-based app would be quicker to develop. On top of that, you can still have your services communicate with each other externally if needed.

To Expose Data

Exposing data or functionality to external clients is one of the most common tasks accomplished by applications. Doing this is simpler through service-oriented architecture since there are no dependencies involved. Since SOA pools all data sources and allows access through one place, it is swift and easy to set up such an application using this architecture.

To Develop Reusable Services

If you are looking to build a reusable service that is small in itself and will probably be a part of a more significant service down the road, you would want to stick with SOA. This is again owed to the more straightforward structure of SOA compared to microservices and the ease in development.

For Apps With High Data Distribution

If you build an app with multiple data sources, including static databases and dynamic APIs, opting for microservices can make things tricky. This is because microservices require you to couple precisely one data source with each service to promote loose coupling. You can do away with multiple data sources with a basic data handling service easily using SOA.

To Develop Highly Available Functions

SOA is quite famous for its high availability and robust nature. If you want to build small but highly available applications or serverless functions, then SOA is the way to go. However, if the size of your app is large, then SOA is not recommended as it will make the app tightly coupled.

When to Choose Microservices Architecture

Here are some cases wherein you should opt for the microservices architecture.

For Projects That Use a Variety of Technologies

If your project uses multiple frameworks, programming languages, and other technologies down the road, you might want to stick with microservices from the beginning. This is because it is one of the very few architectures that support integrating multiple technologies into one project. You can have each of your microservice components built in varying technologies.

For Projects That Already Include a Set List of APIs & Information Exchange Procedures

Microservices generally require a lot of planning since the app has to be broken down into a large number of small parts for development. However, if you have already done this work for a project, or if a project is simple enough that it defines a list of APIs and other information exchange processes, you can go ahead and build it using microservices. This will give you the benefits of microservices along with an increased speed and ease in development.

To Implement Well-Defined Agile Process in Development

Microservices split a more extensive app into smaller but fully functional components. So if you are looking to implement the Agile process of development throughout your project, microservices might be just right for you. Each element of a microservices-based application will go through the complete software development lifecycle and you can easily use Agile in this.

To Utilize Cloud Systems to Their Maximum Potential

Microservices are known for optimization. You can provision hundreds of microservice containers on a cloud and have them scaled up and down easily via container orchestration tools. You can also replace a broken microservice container with a new one instantly. Whereas with other architectures, you don’t get such fine control over your app’s components in DevOps. So if you are looking to make the best use of cloud systems, remember to opt for microservices.

For Cases Where You Know How To Break Down A Large App

This is similar to one of the cases we discussed earlier. If you opt for microservices architecture, you will need to design your application so that it can be broken down into modular, independent components. If you have a loosely coupled project and know how to split it into business components easily, you should opt for microservices.

Closing Thoughts

Application architecture designs offer their unique sets of advantages. Determining the right design for your next big app can be a crucial decision for its growth. The most critical factor in this decision should be the requirements laid out for your application. 

SOA is a method of breaking down large, monolithic apps into smaller modules, while microservices are used to fulfill the same purpose in a more delicate, granular way. Both of these architectures support operations in the cloud which increases flexibility while building and distributing apps.  Both of these styles use automation to speed up operations.

However, both architectures have their well-defined use cases. Larger, diverse organizations tend to lean towards service-oriented architecture due to the support for integration between heterogeneous apps and messaging protocols via the enterprise-service bus (ESB). Smaller organizations and projects do not require such a robust communication layer and are easier to develop with the microservices architecture.

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