When to Use REST web services
You can choose REST web services when your application requires the following.
Quality
REST web services (APIs) offer quality. They are simple and user-friendly. They are flexible, and support many different data formats like JSON, HTML, XML, and YAML. As per your applications, you can also use custom data format.
In REST APIs, JSON is the most widely used data format. JSON is easy to read, has a small file size, is faster, has low data processing, and is good for developers.
CRUD operations
REST is good for CRUD (create, read, update, and delete) operations because it uses the standard HTTP methods that are POST, GET, PUT, and DELETE. POST to add new data, GET to retrieve data, PUT or PATCH to update data, and DELETE to delete data.
Statelessness and scalability
The request contains all the information that the server needs. The server does not store any information about the request. On the server, there is more memory, server can handle more requests.
Support
There is a huge support for the REST APIs. Almost all the popular high-level languages can interact with REST APIs. They have many libraries to work with REST APIs. There are several tools to test and debug the REST APIs. There is support for documentation as well.
Testing and debugging
Tools like Postman and cURL can be used effectively to test and debug the REST APIs. Postman is a very qualitative tool. It also allows us to create and document the REST APIs. Postman is also available for free.
Documentation
There are many good tools available that allow you to easily document the REST APIs. Swagger is a popular free API documentation tool.
Popularity
Very popular, many leading organizations use the REST APIs to let other applications integrate into their services.
When to use SOAP web services
You can choose SOAP web services when your application requires the following.
Security
SOAP web services (APIs) are good for security. They have many strong security features like WS-Security, Message-level security, and Transaction Security. For some organizations, security is a top priority, like Banks, E-commerce platforms, and Payment Gateways.
Data integrity
SOAP APIs ensure there is data integrity. SOAP offers security features that keep the data intact and unchanged when it is transmitted between the systems. XML offers a well-defined structure that keeps the data as it is, accurate.
Error handling
SOAP APIs provide the fault elements to handle the errors. When an error occurs in a request or message, the fault elements provide the details of that error. They help understand and fix the errors.
Legacy systems
In some organizations, many outdated computers only use the SOAP APIs. In these systems, other APIs will not work. Replacing these legacy systems with modern computers that support modern APIs will require some significant investment. So, it is best to continue using the SOAP APIs.