Configuring CORS in FastAPI

FastAPI, an ASGI framework in Python, offers an efficient way to set up Cross-Origin Resource Sharing (CORS) using Starlette's CORS middleware. This tutorial delves into implementing CORS in FastAPI, highlighting its combination of features from Flask, Django-Rest-Framework, Pydantic, and Starlette, which makes it appealing even without using Python's Async capabilities. CORS is a protocol that allows scripts from one domain to access resources on another, achieved through a preflight exchange of headers. The guide critiques the limitations of using regex-based reverse proxies for CORS, suggesting that code-based solutions like FastAPI's middleware offer greater flexibility and security. By default, FastAPI's CORS middleware supports a static list of origins and origin regex, though it can be extended to dynamically manage origins using a database. Implementing CORS in FastAPI is straightforward and can be customized for enhanced flexibility, although users need to be cautious about setting fail-safe options to prevent unintended access. The discussion also touches on performance considerations when using databases for dynamic CORS origin checks and suggests alternatives like in-memory databases to optimize response times.