What are some alternatives?
When comparing Google Cloud Functions and RabbitMQ, you can also consider the following products
Google App Engine - A powerful platform to build web and mobile apps that scale automatically.
IBM MQ - IBM MQ is messaging middleware that simplifies and accelerates the integration of diverse applications and data across multiple platforms.
Dokku - Docker powered mini-Heroku in around 100 lines of Bash
Apache ActiveMQ - Apache ActiveMQ is an open source messaging and integration patterns server.
Azure Web Apps - Create and deploy mission critical Web apps that scale with your business
Apache Kafka - Apache Kafka is an open-source message broker project developed by the Apache Software Foundation written in Scala.