A web application must push stock price updates to thousands of connected users with sub-second latency, in a read-heavy pattern with one writer and many readers. Which AWS service is optimized for this publish-subscribe, real-time delivery pattern?
Show answer and explanation
Answer: D
AppSync subscriptions hold persistent WebSocket connections with browsers and mobile clients, and when the underlying data source updates, AppSync pushes the change to the subscribed clients within milliseconds. Managed real-time push directly to end-user devices, without polling infrastructure, is exactly what a live price feed to a UI needs.
Why the other options are wrong
- A. SQS serves backend consumers that pull messages from queues; browsers cannot connect to a queue, and long polling is not sub-second real-time push.
- B. Kinesis is a durable stream buffer for data pipelines; consumers poll shards, and there is no managed path from the stream to browser or mobile sessions.
- C. SNS delivers to protocols such as HTTP endpoints, email, and mobile push notifications, not persistent WebSocket browser connections, so it still needs an intermediate relay to reach users in web applications.