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Python / Uvicorn Fundamentals Interview Questions

What is ASGI and how does it differ from WSGI?

WSGI (Web Server Gateway Interface) is the original Python standard for web servers and applications. It is synchronous - each request is handled sequentially, blocking while waiting for I/O. This makes it unsuitable for WebSockets, server-sent events, or highly concurrent async applications.

ASGI (Asynchronous Server Gateway Interface) is the modern successor - an async-native interface that supports concurrent connections, WebSockets, HTTP/2, and long-lived connections via Python's asyncio.

WSGI vs ASGI comparison
FeatureWSGIASGI
Execution modelSynchronous (blocking)Asynchronous (non-blocking)
WebSocket supportNoYes
Long-lived connectionsNoYes
Python async/awaitNot nativelyFirst-class support
HTTP/2Not nativelyYes (via compatible servers)
Example serversGunicorn, uWSGIUvicorn, Daphne, Hypercorn
Example frameworksDjango, FlaskFastAPI, Starlette, Django (3.1+)

An ASGI application is an async callable that accepts three arguments: scope (connection metadata), receive (async function to receive messages), and send (async function to send messages). This simple interface enables the server to remain decoupled from the application framework.

Which of the following is a key advantage ASGI has over WSGI?
What are the three arguments an ASGI application callable receives?

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More Related questions...

What is Uvicorn and what problem does it solve for Python web development? What is ASGI and how does it differ from WSGI? How do you install Uvicorn and what is the difference between the minimal and standard installations? How do you run a basic Uvicorn server from the command line? What are Uvicorn's default host, port, and log level settings? What is uvloop and how does it improve Uvicorn's performance? What are httptools and h11, and when would you choose each? How does Uvicorn's --reload flag work and what does it require? How do you run Uvicorn programmatically using uvicorn.run() and uvicorn.Config/Server? What are Uvicorn workers and how do you configure multi-process deployments? How do you deploy Uvicorn with Gunicorn for production? How do you configure SSL/TLS (HTTPS) in Uvicorn? What is the ASGI lifespan protocol and how does Uvicorn support it? How do you configure Uvicorn logging and access logs? What are proxy headers in Uvicorn and how do you configure trusted proxies? How does Uvicorn handle WebSocket connections? What is the --root-path setting in Uvicorn and when do you need it? How do you use Uvicorn with a Unix domain socket instead of a TCP port? What is the --factory flag in Uvicorn and when is it useful? How do you configure Uvicorn with environment variables? What is Uvicorn's --interface flag and what application types does it support? How do you run Uvicorn inside a Docker container? What is the difference between Uvicorn, Hypercorn, and Daphne as ASGI servers? How do you handle graceful shutdown in Uvicorn? What are the key Uvicorn settings for a production-hardened deployment? How do you run Uvicorn with systemd for automatic restarts and log rotation? What is the relationship between Uvicorn and FastAPI? How do you configure Uvicorn's timeout settings? How do you write a minimal ASGI application that works with Uvicorn without any framework? How do you configure Uvicorn's log config file for custom logging formats? What is the --app-dir flag in Uvicorn and when do you need it? How do you test a Uvicorn-served ASGI application without starting the server? What is Granian and how does it compare to Uvicorn as an ASGI server alternative? What is the scope dictionary in the ASGI protocol and what does it contain? What are best practices for deploying Uvicorn in a Kubernetes environment?
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