Lambda is AWS’ realization of a serverless architecture. Instead of deploying instances and scaling them manually, developers deploy only their code and AWS executes the code. Different triggers for code executions can be defined, e.g. when a new event in an AWS Kinesis stream is published or when a REST endpoint is accessed.
Since AWS takes care of Lambda execution, the Lambda does automatically scale in and out to current needs. Coupled with its “pay only for what you use” pricing and the fact that lambda execution can scale to zero when no lambda is executed, AWS Lambda is an interesting technology.