Azure Functions lets you run your code in a serverless environment without having to first create a virtual machine (VM) or publish a web application : Create your first function in the Azure portal | Microsoft Learn.
You must have a function app to host the execution of your functions. A function app lets you group functions as a logical unit for easier management, deployment, scaling, and sharing of resources.
You can create an HTTP trigger function. Don’t forget to manage the Authorization level (i.e. Anonymnous).
You can choose your specific HTTP trigger : Azure Cosmos DB, Blob Storage, etc