You can deploy your application in SAP BTP, Kyma runtime as a Docker container.
You can use any technology of choice as long as you can package it as a Docker container. The Docker container can be built using Cloud Native Buildpacks (CNB). It is also possible to build lightweight Serverless Functions in Python and JavaScript.
With microservices, you build and maintain the Docker image.
When working with Serverless Functions, you write the code and Kyma takes care of creating and deploying the Docker image.