"Serverless" refers to an architecture in which the infrastructure of your applications is managed by cloud providers. Contrary to its name, a serverless application does require a server but it doesn't require you to run and manage it on your own. Instead, you subscribe to a given cloud provider, such as AWS, Azure, or GCP, and pay a subscription fee only for the resources you actually use. Because the resource allocation can be dynamic and depends on your current needs, the serverless model is particularly cost-effective when you want to implement a certain logic that is triggered on demand. Simply, you get your things done and don't pay for the infrastructure that stays idle.

Kyma offers a service (known as "functions-as-a-service" or "FaaS") that provides a platform on which you can build, run, and manage serverless applications in Kubernetes. These applications are called Functions and they are based on Function custom resource (CR) objects. They contain simple code snippets that implement a specific business logic. For example, you can define that you want to use a Function as a proxy that saves all incoming event details to an external database.

Such a Function can be:

• Triggered by other workloads in the cluster (in-cluster events) or business events coming from external sources. You can subscribe to them using a Subscription CR.
• Exposed to an external endpoint (HTTPS). With an APIRule CR, you can define who can reach the endpoint and what operations they can perform on it.