From DevOps to NoOps: 10 Cloud Services You Should Be Using

PubNub offers publish/subscribe messaging as a service and supports real-time, global messaging for cloud and mobile apps. Pusher and Amazon SNS (Simple Notification Service) provide similar services, but PubNub is amazingly quick, getting as close to real-time as the web gets, and is very inexpensive, even for millions of messages. Developers can leverage the PubNub REST API, which is an asynchronous, streaming API.