When fetching a specific post, a 404 HTTP status code should be returned if the post ID doesn't exist, instead of null. This provides better feedback to the frontend. FastAPI's `HTTPException` simplifies error handling, allowing specification of the status code (e.g., 404) and a detailed error message. For POST requests (creating a post), a 201 (Created) status code is preferred over the default 200 (OK). This is achieved by adding `status_code=status.HTTP_201_CREATED` to the path operation decorator.