WSCAT – utility is a convenient tool for testing a WebSocket API
Tutorial: Building a serverless chat app with a WebSocket API, Lambda and DynamoDB
Backends for front end pattern
AWS Document
The backend can send callback messages to connected clients.
Sending messages back to connected clients
Use @Connect command in backend
WebSocket APIs for API Gateway charge for the messages you send and receive. You can send and receive messages up to 128 KB in size. Messages are metered in 32-KB increments, so a 33-KB message is charged as two messages. If larger message is received, connection will close with code 1009.
In addition to paying for the messages you send and receive, you are also charged for the total number of connection minutes.