Google has released an alpha of Cloud Functions, a managed Node.js environment that is reminiscent of Amazon Web Services (AWS)'s Lambda.
Pub/Sub triggers using Google's message bus, called Cloud Pub/Sub. In this scenario, other applications publish messages that are received by the Google Cloud Function.
Cloud Storage notifications. Functions are triggered when objects are added, deleted or modified in Google's Cloud Storage service.
HTTP notifications. Functions are triggered synchronously by an HTTP Post, making it easy to execute them from any platform.
Direct invocation, using a call command in the Cloud Functions CLI (Command Line Interface. This is intended for test and debug.
Other Google applications such as Gmail can send events to Cloud Pub/Sub, so you could for example have a function that was triggered whenever an email was sent or received by a specific mailbox.
Google Cloud Functions is less flexible than AWS Lambda, which supports Java and Python as well as Node.js, but has the advantage of easy integration with Google's other services.
A key feature of both services is that they are fully managed platforms. Scaling is automatic and developers do not need to be aware of the servers on which the service runs. AWS Lambda is able to run substantial applications as well as lightweight functions. In Google's case, it already has App Engine, which supports Java, Python, PHP or Go, so there is less need for Google Cloud Functions to evolve in this direction.
Since it is in alpha, Google Cloud Functions is not generally available, but you can request access. ®