How do we simulate "Real Time" interaction without WebSockets ?

WebSockets allow us to stream additional data from/to client/server beyond the limits of http request/response. This has opened a world of Real Time apps.
Given that keeping Lambda functions running for long time will cost a lot (_because we are billed per 100ms_) we need to consider an _alternative_ approach for sending data to the client _after_ the initial page/data is rendered...

**_Polling**_?

http://stackoverflow.com/questions/12555043/my-understanding-of-http-polling-long-polling-http-streaming-and-websockets