Microservices vs. SOA Comparison

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Picking the right tool for the job makes software development easier and gives your product the best chance of success. The Microservices vs SOA comparison matters to lots of companies since they need to use the most effective way to develop their software applications.

There has been a lot of discussion regarding microservice architecture (MSA) and service-oriented architecture (SOA) in recent years. 

The modularization of software isn‘t a new approach to software development and building software as collections of services has been popular for many years now. 

It could be argued that MSA and SOA have more things in common than actual differences, for example – both depend on services as the main underlying component.

In this blog post, aimed at CTOs, technical leads, and software developers we look at microservices architecture and service-oriented architecture and explore their similarities and differences. 

What is a Service?

Before we get into the nuts and bolts of Microservices vs SOA, it‘s worthwhile to understand what a service is. Developing a “service-centric” software application results in writing code that gets exposed, typically over a network via one of many interfaces.

These interfaces are effectively endpoints to business functionality (services) and regardless of the architectural pattern (SOA, MSA), services tend to share the following attributes:

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• they are self-contained;
• they are “black boxes” to users of the service;
• models a set of activities with specific inputs and outputs, for example, providing customer data, getting weather data, and so on.

These are just some high-level attributes in terms of how service-based software development is approached and with a definition of service out of the way, we can move on to some architectural patterns that leverage services!

Service-Oriented Architecture (SOA)

You can think of SOA as a precursor to microservices architecture, service-oriented architecture (or SOA) exposes collections of functionality, often in the form of web service interfaces that encapsulate complete business functions and processes, all of which serve to make it easier to consume data services and pre-programmed business logic.

The two roles in an SOA application are of a service consumer and a service provider. The consumer layer is the point where users interact with the application and the provider layer contains all the services within an SOA-based application.

One of the main drivers for this architectural pattern is to reduce the complexity that can often be associated with current systems of record.

For example, access to data in existing systems of record often involves having to use code that is fine-grained and exposes too much of the underlying data model. 

Not to forget that consumers of existing systems of record may have to grapple with multiple endpoints or make multiple requests which can make implementing processes or uses cases more complex than it needs to be,

As a service consumer of a service-oriented application, you don‘t need to concern yourself with the underlying operations behind the service interface or the orchestration of the calls you might need to make to satisfy a given use case, all of that is handled for you.

Key takeaway:  The goal of this architectural pattern is to package up functionality into endpoints, typically accessible at the enterprise level that is: easy to access for the business, reusable, and can be used as building blocks for future applications.

Types of SOA services include functional services for business operations, enterprise services to implement functionality, application services for app development, and infrastructure services for non-functional requirements.

Protocols often associated with SOA are advanced messaging queuing protocol (AMPQ), simple object access protocol (SOAP), etc.

Microservices Architecture (MSA)

MSA is in effect, the natural evolution of service-oriented architecture.  At a very high level, microservices are an alternative way for architecting applications that offer a better way to decouple components within an application boundary.  Maybe if microservices were rebranded as microcomponents it‘d be easier to understand!

Monolithic software applications are often broken down into smaller components and as such, introducing microservices architecture can help bring many benefits such as maintainability and improved scalability.

In an application that implements microservices, the application boundaries or interfaces are no different from that of a traditional monolith application, the key difference is what happens behind the application boundary. 

Behind the service boundary, collections of independent microservices run in their own processes, all with their own individual set of APIs or web service endpoints that get exposed through the application boundary. In the image below (courtesy of IBM), you can see a sample of this in action:

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For complete decoupling, isolation, and independence, each microservice can use its own data model that aligns with the domain objects being passed through it which helps improve stability and maintenance.

Best practices you should consider when adopting the microservice architecture pattern

How do you build an effective microservices architecture? You should do the following:

• Analyze whether this is the right architecture pattern for your application. It may not fit your application if you can’t separate the services from each other.
• Define your microservices in such a way that they aren’t too large. At the same time, don’t create too many microservices that are far too small.
• Use the “Domain-Driven Design” (DDD) approach for designing microservices.
• You need to get a buy-in from the senior leadership and the development team early before you implement this architectural pattern. This is important since implementing microservices architecture is a lengthy and complex project.
• Use RESTful APIs to derive maximum value from the microservices architecture. We will discuss RESTful APIs shortly.
• Organize your development team around microservices to gain optimal productivity.
• Plan for separate data storage for each microservice that you design. This prevents coupling between microservices.
• When you develop APIs to implement the microservices architecture, design the APIs based on the business domain.
• DevOps is key to the success of continued development after you have implemented the microservices architecture. Invest in a robust set of DevOps tools and practices.
• Microservices architecture is complex, therefore, you need to invest in a robust monitoring solution.

To learn the best practices for building a microservice architecture, check out our blog post on the topic.

Key takeaway:  Microservice architecture is focused on multiple, independent, self-contained application-level services that are lightweight and have their own unique data model.

Microservices support multiple message protocols. Common messaging protocols used are HTTP, REST, and JMS (Java messaging service).

Service-Oriented Architecture – Attributes

Reusability

One of the main tenets of Service Oriented Architecture was that of code reusability and exposing legacy systems of record and/or business processes as service endpoints.

The vision with SOA is to be able to reuse SOA endpoints across multiple applications across domains, whereas in MSA, a “share-as-little-as-possible” is the main driver.

Business Context

Service descriptions in a service-oriented solution tend to use business descriptions to provide the context in which the service operates.

For example, the name of the business process, the goal, and typically has an interface to achieve this.  Microsoft WCF is a technology that was commonly used to implement service-oriented applications in the early 2000s‘.

Composition

Services within a service-oriented architecture may leverage other services to achieve a business outcome, contrast this with MSA where services are typically independent and self-contained, i.e. no calls to other services. This is a clear SOA microservices difference.

Microservices – Attributes

To help frame the entire comparison in regards to service-oriented architecture vs microservices that we‘re making, it‘s worth detailing some of the main benefits and attributes of MSA again.

Productivity

It can be easier for developers to quickly understand the codebase for a given microservice from end to end due to the smaller codebase. This also has the value-add of being easier to maintain and update which ultimately improves the frequency at which updates to a microservice can be released.

In a service-oriented application, quite often, multiple requests often must be made in order to satisfy business requests.  Throw in a few remote or offshore development teams and your developer productivity could initially take a hit whilst they get used to service-oriented applications architecture.

That said, risks like these can be mitigated during the planning phases of your SOA application development by ensuring the same pool of developers is responsible for a given set of SOA services.

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Resilience

As microservices operate independently of other components, they tend to be resilient, of course, this depends on having a carefully decoupled design to ensure that dependencies are kept to a minimum.

Scalability

Microservices are completely autonomous in their design, generally, make use of their own data model, and often run in their own hosted process.

Development teams can apply updates to discrete microservices without affecting other microservices, additionally, a microservice that is currently experiencing high payloads can be easily relocated to infrastructure if required to free up resources and help further improve scalability.

Microservices vs SOA Architecture

So, how does SOA differ from the microservices architecture? The differences are as follows:

• An SOA component could be a large one, and it might cater to various functions. Companies often use an SOA to bring multiple existing applications under one umbrella (enterprise service bus). On the other hand, microservices are small, and each of them caters to one service only.
• SOA focuses on the reusability of multiple services whereas the microservices architecture focuses on separating the services as independent services.
• In the case of SOA, services communicate using the enterprise bus messaging protocol. On the other hand, the microservices architecture uses APIs for this.
• In the case of SOA, if you change one part of the application, you are updating the entire application. That’s different in the case of the microservices architecture where you change only one microservice.
• Components are shared in the case of SOA, which causes data dependencies. On the other hand, the microservices architecture decouples services, therefore, it eliminates such dependencies.

So, there you have it, microservices vs SOA architecture. In this blog post we‘ve looked at the two approaches to software development, and whilst the modularisation of software isn‘t a new concept, what we‘ve seen is how microservices are in effect a natural evolution from service-oriented architecture. 

That said, service-oriented architecture still has its place and ultimately, the approach you decide to implement will naturally depend on the unique requirements of your software project.

Hopefully, by reading this blog post you‘ve got a better understanding of MSA and SOA and have an awareness of the attributes and benefits of each approach!

If you plan to build a new software application and require expert software developers experienced in various software application architectures, DevTeamSpace can help you via its field-expert software developers’ community. 

All our software developers are vetted for their skills and expertise. You can easily partner with them by sending us your initial project specifications. One of our account managers will get in touch with you to discuss further details on how we can help you.

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