Lesson Complete!
Middleware & Reliability
What you learned
- How middleware wraps every request and response, running code before and after your endpoints
- How to write a logging middleware that records the HTTP method, path, status code, and duration for every request
- Why direct file writes risk data corruption and how atomic writes with
os.replace()prevent it - How the browser's same-origin policy blocks cross-origin requests and how CORS headers allow them
- How to add FastAPI's built-in CORSMiddleware to allow any frontend to call your API
Next up
In the final lesson, you will move hardcoded settings into environment variables using Pydantic's BaseSettings and add a global exception handler that catches any unhandled error and returns a consistent JSON response.