There are many valid use cases for using and implementing Azure functions.
Azure functions use cases
Implementing microservices
Azure functions help in breaking down large applications into smaller discreet functional code units. Each unit is treated independent of the other and evolves in its own life cycle. Each such code unit has its own compute, hardware, and monitoring requirements. Each function can be connected to all other functions. These units are weaved together by orchestrators to build complete functionality. For example, in an e-commerce application, there can be individual functions (code units) each responsible for listing catalogs, recommendations, categories, subcategories, shopping carts, checkouts, payment...