SAA-C03 Q35 · Serverless

Question

A company is developing a serverless, bidirectional chat application that can broadcast messages to connected clients. The application is based on AWS Lambda functions. The Lambda functions receive incoming messages in JSON format. The company needs to provide a frontend component for the application. Which solution will meet this requirement?

Accepted Answer

**Answer C: Amazon API Gateway WebSocket API** is correct because it satisfies every requirement:

1. **Bidirectional communication**: WebSocket APIs maintain persistent, full-duplex connections between the client and server. Unlike HTTP (request-response), the server can push messages to the client at any time without the client needing to poll.

2. **Chat application with broadcasting**: WebSocket API tracks connected clients via **connection IDs**. When a message arrives, a Lambda function can iterate over all connection IDs and push the message to every connected client — this is exactly the broadcast pattern.

3. **Serverless architecture**: API Gateway WebSocket API integrates natively with AWS Lambda. Three route types handle the lifecycle:
   - `$connect` — triggered when a client

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