uvicorn

Uvicorn is refreshingly simple to use in daily development. The basic usage is literally `uvicorn main:app --reload` and you're running. The CLI is intuitive with sensible defaults, and the `--reload` flag makes local development smooth. Configuration options are well-documented and straightforward - setting workers, host, port, or SSL certificates is as simple as adding CLI flags or environment variables.

The error messages are generally clear, especially for common issues like module import errors or invalid ASGI applications. The server logs are clean and informative without being overwhelming. Integration with FastAPI, Starlette, and other ASGI frameworks is seamless since it follows the ASGI spec closely.

The main pain point is the lack of type hints in the programmatic API when embedding Uvicorn in your code. You can call `uvicorn.run()` programmatically, but IDE support is limited and you'll find yourself checking docs frequently. Also, transitioning from development to production requires understanding worker configurations and process managers, which isn't well-covered in the quick-start documentation.

Uvicorn has been my go-to ASGI server for production FastAPI and Starlette deployments. The runtime performance is exceptional - minimal memory overhead and consistently low latency under load. Worker configuration is straightforward with `--workers` flag, and the Gunicorn integration (`gunicorn -k uvicorn.workers.UvicornWorker`) provides robust process management for production.

Configuration flexibility is a major strength. Timeout settings (`--timeout-keep-alive`, `--timeout-graceful-shutdown`) are sensible by default but easily tuned. The `--limit-concurrency` and `--limit-max-requests` options give precise control over resource consumption. Logging integration works well with standard Python logging, and access logs are structured enough for parsing. Graceful shutdown handling is reliable - it properly drains connections during deploys.

The reload behavior during development (`--reload`) is fast and reliable, though watch patterns sometimes need tuning with `--reload-include`. The websocket support is production-ready with proper backpressure handling. One gotcha: the default uvloop event loop (when installed) can mask issues that surface with asyncio, so test both. HTTP/2 support via httptools is solid but requires the h11 fallback for some edge cases.

Getting started with uvicorn is remarkably simple - literally `uvicorn main:app` and you're running. The CLI is intuitive with sensible defaults, and adding reload on file changes is just `--reload`. When you make mistakes like referencing the wrong module path, error messages are clear and point you directly to the problem. The automatic reload during development catches most Python errors immediately.

The documentation is concise but complete, with real examples for common scenarios like running with Gunicorn for production, configuring SSL, and tuning worker processes. The settings page clearly explains each configuration option without burying you in details. I've rarely needed to dig through GitHub issues because most use cases are covered.

Debugging is straightforward - the logging is informative without being noisy, and stack traces are clean. When something goes wrong with your ASGI app, uvicorn's error output clearly separates server issues from application issues. Integration with FastAPI, Starlette, and other ASGI frameworks is seamless, and the performance optimizations (uvloop, httptools) work transparently.