Redbean single-file distributable web server is built using cosmopolitan.
Redbean's home page does a great job of explaining what the software does:
rebean is an open source webserver in a zip executable that runs on six operating systems. The basic idea is if you want to build a web app that runs anywhere, then you download the redbean.com file, put your .html and .lua files inside it using the zip command, and then you've got a hermetic app you can deploy and share.
redbean embeds Lua, SQLite, and MbedTLS into a fork() driven application server that benchmarks at 1.1 million qps on a personal computer. It's got a live bestline REPL with code completion and a UNIX module too, that lets you directly use the Cosmopolitan Libc system call interface. redbean furthermore provides sandboxing and system call tracing for security. This makes redbean a great fit for when you want to build an app that's vertically integrated into a single tiny file that runs on nearly all PCs and servers.
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Deploying a redbean app to Fly from Simon Willison’s TILs
Redbean Tiddlywiki Saver: rpdillon.net; Nov 2022.
shmup/awesome-cosmopolitan: List of Cosmopolitan Libc related resources and projects
Fullmoon is a Fast and minimalistic Redbean-based Lua web framework in one file by Paul Kulchenko, the creator of ZeroBraneStudio, a Lua IDE.