AWS Lambda is an event-driven, serverless computing platform provided by Amazon as a part of Amazon Web Services. It is a computing service that runs code in response to events and automatically manages the computing resources required by that code. It was introduced in November 2014. The purpose of Lambda, as compared to AWS EC2, is to simplify building smaller, on-demand applications that are responsive to events and new information. AWS targets starting a Lambda instance within milliseconds of an event. Node.js, Python, Java, Go, Ruby, and C# are all officially supported. In late 2018, custom runtime support was added to AWS Lambda, giving developers the ability to run a Lambda in the language of their choice. AWS Lambda supports securely running nativeLinux executables via calling out from a supported runtime such as Node.js. For example, Haskell code can be run on Lambda. AWS Lambda was designed for use cases such as image or object uploads to Amazon S3, updates to DynamoDB tables, responding to website clicks or reacting to sensor readings from an IoT connected device. AWS Lambda can also be used to automatically provision back-end services triggered by custom HTTP requests, and "spin down" such services when not in use, to save resources. These custom HTTP requests are configured in AWS API Gateway, which can also handleauthentication and authorization in conjunction with AWS Cognito. Unlike Amazon EC2, which is priced by the hour but metered by the second, AWS Lambda is metered in increments of 100 milliseconds. Usage amounts below a documented threshold fall within the AWS Lambda free tier - which does not expire 12 months after account signup, unlike the free tier for other AWS services. in 2019, at AWS' annual cloud computing conference, the AWS Lambda team announced "Provisioned Concurrency" — "." The Lambda team described Provisioned Concurrency as "ideal for implementing interactive services, such as web and mobile backends, latency-sensitive microservices, or synchronous APIs."
Specification
Each AWS Lambda instance is a container created from Amazon Linux AMIs with 128-3008 MB of RAM, 512 MB of ephemeral storage and a configurable execution time from 1 to 900 seconds. The instances are neither started nor controlled directly. Instead, a package containing the required tasks has to be created and uploaded to an S3bucket and AWS is instructed to run it when an event is triggered. Each such execution is run in a new environment so access to the execution context of previous and subsequent runs is not possible. This essentially makes the instances stateless, all the incoming and outgoing data needs to be stored by external means. The maximum compressed size of a Lambda package is 50 MB with the maximum uncompressed size being 250 MB.
