The API Gateway is a server, playing the role of a single-entry point for all API requests originating from clients, such as web or mobile applications. It lies between the client and the backend services, handling tasks of request routing, composition, and protocol translation. Most of the purpose of an API Gateway is to abstractly create a single central layer that decouples clients from the services they request, allowing for easy development and management of APIs with increased agility.
Some of the primary features and benefits of the API Gateway are as follows:
- Request routing: The API Gateway routes incoming requests to the appropriate backend service by request path, query parameters, or other criteria. This allows clients to expose access to multiple services from a single endpoint without the need to know how any given service may be implemented or deployed.
- Protocol translation: This can be done with the help of API Gateway between the different protocols of communication used by a client and backend service. The protocols can range from HTTP to WebSocket to gRPC. This allows clients and services to use a desired protocol without any compatibility requirement.
- Make the API Gateway transform request and response data: The passing request and response data can be changed by the API Gateway during its flow, for example, to add or remove headers from requests, filter or aggregate data, change the data format of messages, and many other possibilities. This allows the API to present customers an optimized and common interface that serves them whether the backend services are implemented or not.
- Authentication and authorization: The API Gateway ensures incoming request authentication and authorization policies, such as requiring clients to provide valid credentials or access tokens, in order to secure access to the API and avoid access from users unauthorized to consume the backend services.
- Monitoring and Analytics: API Gateway helps in collecting and analyzing the data related to usage of the API and performance, such as request/response metrics, error rates, and latency, among others. It helps to monitor the health and usage of the API, which is useful for developers or operators to be able to optimize it and make improvements if need be.
API Gateways are very common in a microservices architecture, where they facilitate the development and deployment of independent multiple services that need to be composed and accessed through a single, consistent interface. They are also part of serverless architectures, where backend services are implemented as functions that need to be invoked and orchestrated through an event-driven model.
Some of the most popular API Gateway solutions include Amazon API Gateway, Google Cloud Endpoints, Kong, and Tyk. These provide a set of features and integrations either to build and deploy APIs or to manage them, including monitoring, testing, and securing with gateway-level policies. The use of an API Gateway allows businesses to develop APIs and rapidly deliver them. It enables faster and easier scalability, reliability, and security of applications.