What Is Service-Oriented Architecture (SOA)?

SOA focuses on enhancing the reuse of existing computing functions while enabling their combination in various ways to meet business requirements. This architecture’s foundation lies in the loose coupling of services, which implies that they can interact without depending on each other’s inner workings, making the system more adaptable to change.

The SOA architecture was first proposed in 1998 and was formalized by The Open Group in 2007. It was commonly used in the first decade of the 21st century, but has since declined in popularity and was largely replaced by microservices architecture.

What Are Microservices? 

Microservices is an architectural style that structures an application as a collection of small, autonomous services modeled around a business domain. This approach enables the rapid, reliable delivery of large, complex applications. It also allows an organization to easily evolve its technology stack.

Each service in a microservices architecture is self-contained, independent, and serves a unique business goal, enabling continuous deployment and scaling. This modularity allows for flexibility in using different programming languages and frameworks, making microservices especially suited for a polyglot environment. It empowers individual teams, typically each responsible for one microservice, to deploy, scale, and update their portions of the application independently, enhancing agility and reducing time to market.

Microservices is today considered the mainstream architecture for application development. According to an O’Reily report, more than 77% of organizations use microservices, and over 92% of them have experienced success with the architecture.

This is part of a series of articles about DevSecOps.

In this article:

• Is SOA Dead?
• SOA vs. Microservices: Benefits
• SOA vs Microservices Architecture: Key Differences
• Microservices vs. SOA: How to Choose?

Is SOA Dead? 

Despite the widespread adoption of microservices, Service-Oriented Architecture (SOA) remains a viable approach in the modern IT landscape. While its popularity has waned compared to the early 2000s, SOA continues to play a crucial role, especially in large organizations that manage complex, legacy systems requiring robust integration and interoperability capabilities.

According to Verified Market Reports, the global SOA market size, valued at USD 15.9 billion in 2023, is projected to reach USD 29.4 billion by 2030, growing at a CAGR of 9.28% from 2024 to 2030. This growth indicates that SOA is far from obsolete; instead, it reflects the ongoing demand for architectures that can efficiently handle large-scale integrations and ensure interoperability across diverse technology stacks.

SOA’s architecture supports intricate integration scenarios more effectively than microservices, making it particularly beneficial for organizations with extensive legacy systems. It promotes the reusability of existing services, which not only accelerates the deployment of new applications but also enhances overall IT agility—crucial for businesses that need to adapt to market changes swiftly.

In addition, SOA’s standards-based communication protocols aid in facilitating smoother and more secure interactions between disparate systems. This aspect is particularly critical for enterprises operating within regulated industries where data integrity and security are critical.

SOA vs. Microservices: Benefits 

Benefits of Services Oriented Architecture

Service-Oriented Architecture (SOA) offers several benefits that can impact an organization’s IT strategy and business efficiency:

• Interoperability and integration: SOA facilitates easier integration of diverse systems and technologies within an organization or across different organizations, including legacy systems. Its standards-based communication protocols help in connecting systems that would otherwise operate in silos.
• Reusability: By emphasizing modular services that can be reused across many different applications in a large enterprise, SOA reduces development time and costs. This approach maximizes the value of existing investments in technology and minimizes redundancy.
• Flexibility: SOA’s loose coupling of services allows for greater flexibility in responding to changing business needs. Organizations can quickly adapt their IT systems to support new processes or products without extensive rework.
• Scalability: SOA enables organizations to scale their IT solutions more easily. Services can be added or expanded independently to meet growing demands, without disrupting the existing infrastructure.
• Cost efficiency: Over time, the reuse and interoperability features of SOA can lead to significant cost savings. By leveraging existing services and facilitating smoother integration, organizations can avoid the costs associated with developing new solutions from scratch.
• Alignment with business processes: SOA encourages the alignment of IT infrastructure with business goals. By designing services that reflect business processes, organizations can ensure that their IT systems are directly contributing to business objectives.

Benefits of Microservices Architecture

Microservices architecture brings its own set of benefits, particularly suited for dynamic and complex application landscapes:

• Enhanced scalability: Microservices can be scaled independently, allowing for more precise resource allocation. This is especially useful in cloud environments where resources can be adjusted dynamically according to the load.
• Resilience: The decentralized nature of microservices enhances fault isolation. If one microservice fails, it does not necessarily compromise the entire system, thus ensuring higher availability and reliability.
• Simplified deployment: With microservices, deployment is simplified since each service can be deployed independently. This reduces the complexity and risk associated with deploying large, monolithic applications.
• Improved performance: Because individual components can be scaled as needed, microservices applications can operate faster to meet user expectations. This granular scalability is particularly beneficial in managing varying workloads and optimizing resource usage.
• Technological freedom: Teams can choose the best technology stack for their specific microservice, enabling the use of the latest and most suitable technologies. This polyglot approach can lead to more innovative and effective solutions.
• Faster time to market: Independent development and deployment of services mean that updates and new features can be released more quickly. This agility supports a faster response to market changes or customer demands.
• Suitable for cloud native environments: Microservices are designed to capitalize on the benefits of cloud computing delivery models. Cloud-native technologies, such as containers, service meshes, microservices, immutable infrastructure, and declarative APIs, make microservices easier to develop, deploy, and manage.

SOA vs Microservices Architecture: Key Differences 

1. Implementation

SOA generally employs an Enterprise Service Bus (ESB), which adds a level of complexity in managing service interactions. It relies on this centralized bus to manage communications, routing, and orchestration between different services. In contrast, microservices architecture uses a decentralized approach, where each service communicates directly with others through well-defined APIs, reducing reliance on a central mechanism for integration.

This direct communication in microservices simplifies the architecture, making it easier to implement and manage compared to the more centralized and complex nature of SOA.

2. Communication

SOA architectures often rely on heavyweight protocols like SOAP for cross-service communication, requiring extensive data parsing and transformation. This can lead to performance bottlenecks as systems scale. Microservices, however, favor lightweight protocols such as REST or gRPC, which are more efficient and conducive to the high-speed communication needed for today’s web and mobile applications.

By using these simpler, faster protocols, microservices architectures can achieve more scalable and responsive applications, accommodating modern user expectations and workloads.

3. Data Storage

In SOA, data is commonly stored in a shared, centralized database accessed by all the services. This approach may ease data management but can also create bottlenecks and hinder performance as the system scales. Microservices architectures embrace a decentralized approach to data storage, with each service managing its own database.

This separation ensures service independence, improving fault isolation and enabling services to be scaled or updated without impacting others. However, it introduces complexity in maintaining data consistency and integrity across services.

4. Scalability

SOA architectures are scalable but can be limited due to their centralized nature, particularly with an ESB in place. The scalability often relies on scaling the ESB, which can become a single point of failure. Microservices inherently support scalability due to their modular nature. Individual components can be scaled independently based on demand, allowing for more granular control over resources and improved application responsiveness.

This independent scaling capacity makes microservices ideal for cloud environments, where resources can be dynamically adjusted to match fluctuating loads.

5. Remote Services

SOA allows for remote service calls but often incurs significant overhead due to its complex communication protocols and reliance on ESBs. These characteristics can degrade performance, especially for distributed applications. Microservices minimize this overhead by employing simpler, more direct communication methods and avoiding the need for a central mediation layer.

This approach enhances the feasibility and performance of remote service calls in microservices architectures, facilitating more efficient and scalable distributed applications.

6. Governance

SOA requires robust governance to ensure that services comply with enterprise standards, given its centralized configuration and the extensive reuse of shared services. This often necessitates a significant investment in monitoring, policy enforcement, and management tools. Microservices, by being decentralized, push governance to the service level, relying on conventions over centralized control.

While this reduces the overhead for governance at the macro level, it places more responsibility on individual development teams to adhere to agreed standards and practices.

7. Deployment

Deployment in SOA environments tends to be monolithic, with updates to one service potentially requiring redeployment of others. This can slow down the release cycles and complicate rollback procedures. Meanwhile, microservices are deployed independently, allowing for faster iterations and simpler rollback processes if a service update fails.

This independence significantly reduces the risk associated with deploying changes and accelerates the delivery of new features or updates.

Microservices vs. SOA: How to Choose? 

First, we should say that in the 2020s, the default choice for a software project is microservices, because of its improved flexibility, efficiency, and compatibility with cloud native environments. However, some organizations might still consider the older SOA architecture for specific use cases:

• Scope and size of project: Microservices are ideal for large-scale applications with complex requirements that need rapid scaling, while SOA might be better suited for simpler or legacy applications used in large organizations, where the emphasis is on integration and efficient utilization of existing resources.
• Organizational capability: Implementing microservices requires a strong DevOps culture and proficiency in continuous integration and continuous deployment practices. Organizations without this capability may find SOA a more manageable approach.
• Technology stack compatibility: If an organization has a diverse technology stack and requires flexibility in programming languages and tools, microservices offer an advantageous approach. Conversely, SOA works well in more homogeneous and standardized environments.
• Need for scalability: Microservices provide better options for scaling components independently, which is crucial for applications experiencing variable loads. SOA can facilitate scalability but usually within the constraints of more centralized management systems.
• Complexity and cost of maintenance: While microservices simplify deployment and scaling, they can increase complexity in managing multiple small components and their interactions. SOA, although potentially cumbersome to set up, could be more straightforward to maintain due to its centralized nature.
• Long-term strategic goals: If the goal is to achieve a highly agile environment that can quickly adapt to market changes, microservices are preferable. However, if the aim is to maximize the reuse of existing assets and ensure robust enterprise-wide service integration, SOA might be more beneficial.
• Leveraging cloud native technology: If the organization is migrating to the public cloud, or using cloud native technology like containers on-premises, microservices should be preferred because they were designed with cloud native environments in mind. SOA architectures can be implemented in a cloud native environment, but cannot leverage many of the benefits of modern cloud computing.