Learn AWS Serverless Computing

Ephemeral state

So, that's how a function can be invoked. What happens when the code finishes executing? When this happens, the function runtime is terminated. This includes access to the memory state and any temporary files that were created on the filesystem. In other words, everything is gone – state included. This means that if you need to maintain or keep track of a state, then this should be saved to a service that's external to the function, such as Amazon DynamoDB.

Consult the DynamoDB developer guide to learn more about how to persist state (see the link in the Further reading section), or check out Chapter 5, Leveraging AWS Services, where we will leverage other AWS services with Lambda.

Functions also have a finite execution time. ...