Serverless and PaaS

Serverless is often confused with Platform as a Service (PaaS). PaaS is a kind of cloud computing model that allows developers to launch applications without worrying about the infrastructure. According to this definition, they have the same objective! And they do. Serverless is like a rebranding of PaaS, or you can call it the next generation of PaaS.

The main difference between PaaS and serverless is that in PaaS you don't manage machines, but you are billed by provisioning them, even if there is no user actively browsing your website. In PaaS, your code is always running and waiting for new requests. In serverless, there is a service that is listening for requests and will trigger your code to run only when necessary. This is reflected in your bill. You will pay only for the fractions of seconds that your code was executed and the number of requests that were made to this listener. Also, serverless has an immutable state between invocations, so it's always a fresh environment for every invocation. Even if the container is reused in a subsequent call, the filesystem is renewed.