The main differences between Service-Oriented Architecture (SOA) and Microservices can be summarized across several key aspects:
1. Scope and Granularity
SOA: SOA is designed with an enterprise-wide scope, focusing on integrating various services across the entire organization. It typically involves larger, more coarse-grained services that are reused across multiple applications[7][8].
Microservices: Microservices architecture focuses on building applications as a collection of small, fine-grained, and independently deployable services. Each microservice is designed to handle a specific business function and operates within a bounded context[1][2][5].
2. Service Independence and Coupling
SOA: Services in SOA are loosely coupled but often share resources and data, which can lead to dependencies between services. This can make the system more complex and slower to deploy changes[1][3][4].
Microservices: Microservices are highly independent and loosely coupled. Each service has its own database and is designed to be autonomous, which reduces dependencies and allows for faster deployment and scaling[1][2][5].
3. Communication Protocols
SOA: SOA typically uses a variety of communication protocols, including SOAP (Simple Object Access Protocol), AMQP (Advanced Message Queuing Protocol), and others. This heterogeneity supports interoperability but can add complexity[1][3][4].
Microservices: Microservices primarily use lightweight protocols such as REST (Representational State Transfer) and simple messaging protocols like HTTP and JSON. This homogeneity simplifies communication and integration[1][3][4].
4. Data Management
SOA: In SOA, services often share a common data storage layer, which can lead to issues with data consistency and governance across the enterprise[4][8].
Microservices: Each microservice manages its own data, which promotes data autonomy and reduces the risk of data-related dependencies. However, this can also lead to data duplication and challenges in maintaining data consistency[4][8].
5. Deployment and Scalability
SOA: Deploying and scaling services in SOA can be more complex because services are often interdependent. Adding or updating a service may require redeploying the entire application[1][3][4].
Microservices: Microservices can be deployed and scaled independently, which allows for more agile and flexible development. This independence also enhances fault tolerance, as the failure of one service does not necessarily impact the entire application[1][2][5].
