Service Oriented Architecture (SOA) to Microservice

 Service-oriented architecture (SOA) is a method of software development that uses software components called services to create business applications. Each service provides a business capability. They can also communicate with each other across platforms and languages. Developers use SOA to reuse services in different systems or combine several independent services to perform complex tasks. 

Microservices architecture is an evolution of the SOA architectural style. While each SOA service is a full business capability, each microservice is a much smaller software component that specializes in a single task only. Microservices address the shortcomings of SOA to make the software more compatible with modern cloud-based enterprise environments.

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.

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.