What are some alternatives?
When comparing NATS and CloudAMQP, you can also consider the following products
Firebase - Firebase is a cloud service designed to power real-time, collaborative applications for mobile and web.
RabbitMQ - RabbitMQ is an open source message broker software.
Socket.io - Realtime application framework (Node.JS server)
Apache Kafka - Apache Kafka is an open-source message broker project developed by the Apache Software Foundation written in Scala.
SignalR - SignalR is a server-side software system designed for writing scalable Internet applications, notably web servers.
Amazon SQS - Amazon Simple Queue Service is a fully managed message queuing service.