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An API gateway is programming that sits in front of an application programming interface (API) and acts as a single point of entry for a defined group of microservices. Because a gateway handles protocol translations, this type of front-end programming is especially useful when clients built with microservices make use of multiple, disparate APIs.
A major benefit of using API gateways is that they allow developers to encapsulate the internal structure of an application in multiple ways, depending upon use case. This is because, in addition to accommodating direct requests, gateways can be used to invoke multiple back-end services and aggregate the results.
Because developers must update the API gateway each time a new microservice is added or removed, it is important that the process for updating the gateway be as lightweight as possible. This is why when evaluating API gateways, it's important for developers to look at features the vendor has added to differentiate its product from the competition.
In addition to exposing microservices, popular API gateway features include functions such as: