SOA vs Microservices

What limitations of monolithic architecture does SOA architecture solve?

In monolithic architecture, developers write code for all service functions in a single code base. With service-oriented architecture (SOA), developers can address the challenges of the monolithic architecture, such as the following:

• Scaling challenges that require the entire application to scale, even if only a specific component needs additional resources.

• The inability to add or modify features flexibly, as functionality is distributed across the code base.

• The inability to reuse components across different applications.

• Limited fault tolerance. Failure in one component can potentially bring down the entire system.

• The challenge of adopting new technologies or integrating with external systems that use different technologies.

Monolithic architectures also centralize ownership and development teams responsible for the entire application. They face challenges with continuous delivery and DevOps practices due to the size and complexity of the architectures.

With SOA, developers break down the software functionalities into service provider and service consumer layers. These layers communicate and exchange data through an enterprise service bus (ESB). Developers use SOA to simplify complex applications into multiple reusable services.

What limitations of SOA architecture does the microservices architecture solve?

While service-oriented architecture (SOA) might work well for building large enterprise applications, it needs more flexibility to scale smaller, business-specific applications. These are some limitations of SOA:

• The enterprise service bus (ESB) connects multiple services together, which makes it a single point of failure.

• All services share a common data repository. This makes the services difficult to manage individually.

• Every service has a broad scope. So, if one of the services fails, the entire business workflow will be affected.

So, developers turn to microservices architecture for a more fine-grained approach to building applications.

The microservice model divides an SOA service into smaller services. Each microservice operates within its bounded context and runs independently from other services. In short, the microservices architecture has limited or no interdependencies between individual services and reduces the risk of system-wide failure.

Architectural differences: SOA vs. microservices

Service-oriented architecture (SOA) encompasses a broader enterprise scope. Different business units collaborate efficiently on a common data-sharing platform. In contrast, microservices apply to a narrower scope.

For example, inventory management would be an SOA service of an ecommerce system. But the microservice approach would break inventory management down into smaller services, such as availability checker, fulfillment, and accountings.

Implementation

The SOA implementation involves integrating different types of services into an application. It uses an enterprise service bus to connect service types, like these:

• Functional services to support specific business operations

• Enterprise services to expose a particular business functionality to other services

• Application services used by developers for building and deploying applications

• Infrastructure services to manage nonfunctional features, such as authentication and security

In contrast, the microservices architecture is a more granular and independent implementation of SOA. Microservices do not share resources like SOA services do. Each microservice operates independently to provide very specific functionalities.

Communication

In order to access remote services, the SOA architecture uses a centralized enterprise service bus (ESB) to connect diverse services with multiple messaging protocols. Some of these protocols include SOAP, Advanced Messaging Queuing Protocol (AMQP), and Microsoft Message Queuing (MSMQ). If the ESB fails, all SOA services will be impacted.

Meanwhile, microservices architectures use simpler messaging systems, such as RESTful APIs, Java Message Service (JMS), or publish-subscribe (pub/sub) event streaming. These methods don’t require the microservices to maintain an active connection when they exchange data.

APIs are a common tool for microservices architectures. An API allows two or more microservices to exchange data directly without going through a centralized channel. However, it can create complex data pathways among dozens of microservices, which developers monitor and manage.

Data storage

The SOA environment comprises a single data storage layer shared by other connected services. Different enterprise applications access and reuse the same data in SOA implementations, which optimizes the value of data repositories.

In contrast, each microservice has its own data storage. In microservices architectures, data independence is more important than reusability.

Deployment

It can be challenging to deploy SOA services because they’re coupled to a certain degree. For example, developers must rebuild the entire application if they modify or add a new service. Besides, SOA applications cannot take full advantage of containerization, which abstracts the application from operating systems and hardware.

Meanwhile, microservices are easier to deploy as they are designed to scale in the cloud environment. Each microservice is an independent applicaiton that developers can containerize and deploy on the cloud.

Key benefits: microservices vs. SOA

Both service-oriented architecture (SOA) and microservices allow development teams to build, deploy, and manage modern applications efficiently for cloud environments. That said, microservices offer certain advantages over SOA deployments.

Reusability

One of the principles in SOA designs is an emphasis on reusability and component sharing. In this architecture, multiple front-facing applications use the same SOA services. For example, an invoicing and order-tracking dashboard can access the same service to retrieve customer details.

Meanwhile, microservices take a different approach. They apply data duplication instead of sharing common resources. This way, a microservices-based application performs more efficiently and isn’t confined to the data operations of other services.

Speed

SOA might offer decent speed in simple implementations, but data latency increases as developers add more services to the system. All services compete for the same communication resources and data capabilities.

In contrast, microservices architectures remain agile and responsive as the system scales because they don’t share overlapping resources. Developers can assign and increase compute resources to a specific microservice if traffic demand grows. This allows a microservice-based application to run at an acceptable speed at all times.

Governance flexibility

SOA-based applications provide consistent data governance across common repositories used by different services.

However, developers working with microservices can decide on different governance policies for independent data storage units. Development teams collaborate more efficiently and have freedom to determine data governance mechanisms.

When to use: SOA vs. microservices

Service-oriented architecture (SOA) and microservices provide different ways for organizations to migrate from a monolithic architecture to cloud environments. Depending on certain factors, one might be more suitable than the other in practical use cases.

SOA

Organizations with legacy or stand-alone enterprise applications benefit from the SOA architecture. SOA simplifies conventional software programs into smaller modular parts. It also pools shared resources to streamline business functionalities. Rather than building overlapping and redundant services, developers can reuse existing SOA services to implement more business solutions.

Microservices

Microservices architecture is the better option to support agile development teams. Developers can make rapid and incremental code changes without affecting the application’s stability by using continuous integration and continuous delivery (CI/CD) tools. Microservices are better when developers have these goals:

• Use different programming languages, libraries, or frameworks to build a single application

• Combine individual services built with different software frameworks

• Provision compute resources and scale individual services in real time

With microservices, companies can benefit from modern cloud capabilities and deploy hundreds of microservices with ease.

Summary of differences: SOA vs. microservices

	SOA	Microservices
Implementation	Different services with shared resources.	Independent and purpose-specific smaller services.
Communication	ESB uses multiple messaging protocols like SOAP, AMQP, and MSMQ.	APIs, Java Message Service, Pub/Sub
Data storage	Shared data storage.	Independent data storage.
Deployment	Challenging. A full rebuild is required for small changes.	Easy to deploy. Each microservice can be containerized.
Reusability	Reusable services through shared common resources.	Every service has its own independent resources. You can reuse microservices through their APIs.
Speed	Slows down as more services are added on.	Consistent speed as traffic grows.
Governance flexibility	Consistent data governance across all services.	Different data governance policies for each storage.