The service starts running a programmer's code within milliseconds of an event such as an image upload, in-app activity, website click, or output from a connected device. Programmers can also use AWS Lambda to create new back-end services where compute resources are automatically triggered based on custom requests. Billing is metered in increments of 100 milliseconds, making it cost-effective and easy to scale automatically from a few requests per day to thousands per second.
Lambda runs code on high-availability compute infrastructure and performs all the administration of the compute resources, including server and operating system maintenance, capacity provisioning and automatic scaling, code and security patch deployment, and code monitoring and logging. All programmers need to do is supply the code.
The service essentially provide a virtual space for programmers to run scripts or business logic programs that can be activated when some event occurs.
For those running multiple AWS services as a single operation, coordinating these services usually involves running a program on a full Amazon virtual machine (VM). Lambda does away with the need to run a separate VM or install and maintainthe software needed to run the program. Instead, Lambda provides just a language runtime environment for running just the program itself.
Programmers can AWS Lambda to respond to table updates in Amazon DynamoDB, modifications to objects in Amazon S3 buckets, messages arriving in an Amazon Kinesis stream, AWS API call logs created by AWS CloudTrail, and custom events from mobile applications, web applications, or other web services.
Amazon says AWS Lambda operates the compute infrastructure and has been designed to provide 99.99% availability for both the service itself and for the functions it operates. There are no maintenance windows or scheduled downtimes.
Lambda was annoucned at Amazon's Re:Invent conference during a keynote session. The company is offering a preview of the service and expects to offer the full commercial version in 2015.