Answer: WebSocket APIs

WebSocket APIs In a WebSocket API, the client and the server can both send messages to each other at any time. Backend servers can easily push data to connected users and devices, avoiding the need to implement complex polling mechanisms. For example, you could build a serverless application using an API Gateway WebSocket API and AWS Lambda to send and receive messages to and from individual users or groups of users in a chat room. Or you could invoke backend services such as AWS Lambda, Amazon Kinesis, or an HTTP endpoint based on message content. You can use API Gateway WebSocket APIs to build secure, real-time communication applications without having to provision or manage any servers to manage connections or large-scale data exchanges. Targeted use cases include real-time applications such as the following: Chat applications Real-time dashboards such as stock tickers Real-time alerts and notifications API Gateway provides WebSocket API management functionality such as the following: Monitoring and throttling of connections and messages Using AWS X-Ray to trace messages as they travel through the APIs to backend services Easy integration with HTTP/HTTPS endpoints Incorrect options: REST or HTTP APIs REST APIs - An API Gateway REST API is made up of resources and methods. A resource is a logical entity that an app can access through a resource path. A method corresponds to a REST API request that is submitted by the user of your API and the response returned to the user. For example, /incomes could be the path of a resource representing the income of the app user. A resource can have one or more operations that are defined by appropriate HTTP verbs such as GET, POST, PUT, PATCH, and DELETE. A combination of a resource path and an operation identifies a method of the API. For example, a POST /incomes method could add an income earned by the caller, and a GET /expenses method could query the reported expenses incurred by the caller. HTTP APIs - HTTP APIs enable you to create RESTful APIs with lower latency and lower cost than REST APIs. You can use HTTP APIs to send requests to AWS Lambda functions or to any publicly routable HTTP endpoint. For example, you can create an HTTP API that integrates with a Lambda function on the backend. When a client calls your API, API Gateway sends the request to the Lambda function and returns the function's response to the client. Server push mechanism is not possible in REST and HTTP APIs.

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