What are some alternatives?
When comparing twitter.github.io Kestrel and AWS Lambda, you can also consider the following products
RabbitMQ - RabbitMQ is an open source message broker software.
Google App Engine - A powerful platform to build web and mobile apps that scale automatically.
CloudAMQP - CloudAMQP automates every part of setup, running and scaling of RabbitMQ clusters. Available on all major cloud and application platforms.
OpenShift - OpenShift gives you all the tools you need to develop, host and scale your apps in the public or private cloud. Get started today.
Amazon SQS - Amazon Simple Queue Service is a fully managed message queuing service.
Heroku - Agile deployment platform for Ruby, Node.js, Clojure, Java, Python, and Scala. Setup takes only minutes and deploys are instant through git. Leave tedious server maintenance to Heroku and focus on your code.