Yesterday I opensourced my chatting application I have been developing on and off since late 2021: https://github.com/aolo2/chat
It features a fully custom websocket server built in C using io_uring, and a custom on-disk database (if you can call it that).
There's also a media upload server which is also written from scratch in C on io_uring.
The client is a web UI, which I built in js with no libraries. Here's me scrolling back in time by holding PageUp and searching in a channel with about 10K messages