What is AWS Lambda?

Lambda lets you run functions in response to events, without keeping your own server process running all the time. An event can be an API request, a file being added or a message from a queue. The provider starts the necessary executions within the service's configuration and limits.

For example, after a document is added, a function can read its metadata and request classification. But remember the limited time of a single standard execution, network access, permissions and database connections. Lambda doesn't automatically mean no start-up delays or zero cost of waiting. Long work can be split into stages that save progress.