Microservices vs. SOA: 4 Key Differences and How to Choose

What Are Microservices? 

A microservices architecture is a method of developing software systems that are split into multiple, independent, and small modules. These modules, or ‘services,’ run in their own process and communicate with each other using lightweight mechanisms, often HTTP resource APIs. Each service is fully functional and independently deployable, often owned by a small team.

The microservices architecture advocates for dividing a single application into a suite of small services, each running its process and communicating with lightweight mechanisms. These services are built around business capabilities and independently deployable by fully automated machinery. Moreover, there is a bare minimum of centralized management of these services.

Microservices come with several advantages. They provide flexibility in using technologies and scalability as per the requirement. They also offer better fault isolation: if one microservice fails, the others will continue to work. However, managing, monitoring, and debugging microservices can be complex.

What Is SOA? 

Service Oriented Architecture (SOA) is an architectural pattern in which application components provide services to other components. This is done through a communication protocol, served over a network. The principles of SOA are vendor-agnostic and can apply to any vendor, product, or technology.

SOA is all about reusing and sharing. This architecture is designed to enhance the efficiency of existing IT systems while adding new functionalities. In SOA, services use protocols which describe how they communicate with each other, involving specific policies and contracts.

SOA was intended to allow greater agility. Since services are reused, the business can adapt to changing conditions and requirements more quickly. However, it can be challenging to implement SOA effectively due to the high upfront cost, the need for a shift in corporate culture, and the necessity of a high level of discipline to maintain service interfaces and quality over the long term.

Microservices vs SOA: Key Differences 

1. Design Philosophy and Principles

  • Microservices are all about breaking down an app into its smallest components, then developing and deploying each independently. The focus is on ‘bounded context,’ where each service has its own database and domain logic.
  • SOA emphasizes reusability. Services are designed to be reused across multiple applications and are typically larger and more general purpose. The focus is on ‘shared context’, where different applications share the same services.

2. Service Size, Granularity, and Independence

  • Microservices are small, fine-grained, and independently deployable services. They focus on doing one thing well and are loosely coupled. This allows for a high degree of independence and flexibility, but can lead to complexities in coordinating and managing these services.
  • SOA is typically composed of large, coarse-grained, interdependent services. These services are tightly coupled, which can lead to better coordination but less flexibility. They are designed to be reused by many different applications across the entire enterprise.

3. Communication, Data Management, and Service Coordination

  • In Microservices, each service has its own database, or its own set of tables within a database, and communicates via lightweight, language-agnostic APIs. This provides a high degree of isolation and allows each service to evolve independently, but can also lead to difficulties in managing data consistency and integrity.
  • In SOA, services typically share databases and communicate through an Enterprise Service Bus (ESB) or similar middleware. This can lead to better data consistency and integrity, but can also lead to a higher degree of coupling and make it more difficult for services to evolve independently.

4. Architecture and General Design

  • In Microservices, the architecture is driven by simplicity and decentralization. A pattern such as the Tolerant Reader is often used, encouraging services to ignore the parts of a message they don’t understand, increasing resilience and allowing for easier evolution of services. It uses simple protocols for communication, trying to minimize the complexity that can arise from centralized standards. This architectural style is a reaction against the difficulties and complexities often encountered in SOA.
  • In SOA, the architecture is often centered around an Enterprise Service Bus (ESB) or similar middleware, which can increase complexity, especially when used to integrate monolithic applications. This style often results in centralized governance models and standards that can be overly complex and inhibit change. However, some implementations of SOA can resemble microservices, leading to the view that microservices might be a form of SOA “done right.”

5. Deployment, Scaling, and Evolution

  • In Microservices, each service can be deployed, scaled, and evolved independently. This allows for faster deployment cycles, more granular scaling, and the ability to evolve services independently to meet changing business needs.
  • In SOA, services are typically deployed together as part of a monolithic application. This can lead to longer deployment cycles, less granular scaling, and more complex development cycles. However, it can also lead to better coordination and consistency across services.

When to Use SOA vs. Microservices 

Use Cases Best Suited for SOA

SOA is best suited for large, complex business processes that require integration of diverse applications, often in legacy systems. It’s ideal for organizations that require a high level of reuse and sharing of services across different applications.

For instance, SOA is often used in large enterprises where different departments need to share the same services. It’s also commonly used in scenarios where different businesses need to integrate their systems.

Use Cases Best Suited for Microservices

Microservices are best suited for rapidly evolving, high-scale applications where speed of delivery is critical. They’re ideal for organizations that need to rapidly innovate and scale their applications.

For example, microservices are often used in eCommerce applications where different services (like user management, product catalog, and order management) need to scale independently based on their individual needs. They’re also commonly used in cloud-native applications where rapid deployment and scaling are essential.

How to Choose?

The choice between SOA and Microservices often comes down to your specific needs and context. Here are some factors to consider:

  • Modern architecture: Microservices is a more modern architecture, supported by a wide range of tools and technologies, especially in the cloud native space. Prefer microservices if you are building a new application and want to use the latest technologies, especially if your application is cloud native. 
  • Size and complexity of your systems: If you have a large, complex system that requires integration of diverse applications, SOA might be a better choice. If you have a smaller, more focused application that needs to scale and evolve rapidly, microservices might be more suitable.
  • Need for reuse and sharing: If you need a high level of reuse and sharing of services across different applications, SOA might be a better fit. If you need each service to evolve independently, microservices might be a better choice.
  • Cultural and organizational fit: SOA requires a high level of discipline and a shift in corporate culture to be successful. Microservices require a high level of decentralization and autonomy. Make sure to consider whether your organization is ready for these changes.

Learn more in our detailed guide to microservices architecture

Microservices Delivery with Codefresh

Codefresh helps you answer important questions within your organization, whether you’re a developer or a product manager:

  • What features are deployed right now in any of your environments?
  • What features are waiting in Staging?
  • What features were deployed on a certain day or during a certain period?
  • Where is a specific feature or version in our environment chain?

With Codefresh, you can answer all of these questions by viewing one dashboard, our Applications Dashboard that can help you visualize an entire microservices application in one glance:

Codefresh applications dashboard

The dashboard lets you view the following information in one place:

  • Services affected by each deployment
  • The current state of Kubernetes components
  • Deployment history and log of who deployed what and when and the pull request or Jira ticket associated with each deployment

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