Function as a Service (FaaS) plays a pivotal role in modern development environments, and Firebase's Cloud Functions offers a robust serverless framework with callable and event-driven architecture. This article demonstrates how to utilize Clerk for securing Firebase Cloud Functions, ensuring that only authenticated users can access results, while leveraging the Firebase web SDK and the latest Firebase Callable Functions. The integration between Clerk and Firebase enables seamless user authentication recognized by both systems, without requiring additional backend code or API calls. The example function presented checks for user authentication before processing requests and returns a message including the user identifier. The setup allows developers to invoke the function from client applications using the Firebase web SDK, with Clerk managing authentication through a token representing a valid Firebase user. This approach maintains consistency between user identifiers and simplifies authentication, while benefiting from Clerk's advanced user management features like intuitive UIs and comprehensive user profiles.