Exposing business functionalities as managed services or APIs has become a key requirement

of the modern enterprise architecture. However, web services/SOA is not really the ideal

solution to cater to such requirements, due to the complexity of the Web Service-related

technologies such as SOAP (used as the message format for inter-service communication), WSSecurity (to secure messaging between services), WSDLs (to define the service contract), etc.,

and the lack of features to build an ecosystem around APIs (self-servicing, etc.)

• Therefore, most organizations put a new API Management/API Gateway layer on top of the

existing SOA implementations. This layer is known as the API façade, and it exposes a simple

API for a given business functionality and hides all the internal complexities of the ESB/Web

Services layer. The API layer is also used for security, throttling, caching, and monetization.

https://microservices.io/patterns/apigateway.html