SOAP vs REST - Difference Between API Technologies - AWS

SOAP is a protocol, while REST is an architectural style. This creates significant differences in how SOAP APIs and REST APIs behave.

Design

The SOAP API exposes functions or operations, while REST APIs are data-driven. For example, consider an application with employee data that other applications can manipulate. The application’s SOAP API could expose a function called CreateEmployee. To create an employee, you would specify the function name in your SOAP message when sending a request.

However, the application’s REST API could expose a URL called /employees, and a POST request to that URL would create a new employee record.

Flexibility

SOAP APIs are rigid and only allow XML messaging between applications. The application server also has to maintain the state of each client. This means it has to remember all previous requests when processing a new request.

REST is more flexible and allows applications to transfer data as plain text, HTML, XML, and JSON. REST is also stateless, so the REST API treats every new request independently of previous requests.

Performance

SOAP messages are larger and more complex, which makes them slower to transmit and process. This can increase page load times.

REST is faster and more efficient than SOAP due to the smaller message sizes of REST. REST responses are also cacheable, so the server can store frequently accessed data in a cache for even shorter page load times.

Scalability

The SOAP protocol requires applications to store the state between requests, which increases bandwidth and memory requirements. As a result, it makes applications expensive and challenging to scale.

Unlike SOAP, REST permits stateless and layered architecture, which makes it more scalable. For example, the application server can pass the request to other servers or allow an intermediary (like a content delivery network) to handle it.

Security

SOAP requires an additional layer of WS-Security to work with HTTPS. WS-Security uses additional header content to ensure only the designated process in the specified server reads the SOAP message content. This adds communication overheads and negatively impacts performance.

REST supports HTTPS without additional overheads.

Reliability

SOAP has error handling logic built into it, and it provides more reliability. On the other hand, REST requires you to try again in case of communication failures, and it’s less reliable.