What are some alternatives?
When comparing Google Cloud Functions and ZeroMQ, you can also consider the following products
Google App Engine - A powerful platform to build web and mobile apps that scale automatically.
Apache Kafka - Apache Kafka is an open-source message broker project developed by the Apache Software Foundation written in Scala.
Dokku - Docker powered mini-Heroku in around 100 lines of Bash
RabbitMQ - RabbitMQ is an open source message broker software.
Azure Web Apps - Create and deploy mission critical Web apps that scale with your business
Amazon SQS - Amazon Simple Queue Service is a fully managed message queuing service.