GoatCounter is an open source web analytics platform available as a hosted service (free for non-commercial use) or self-hosted app. It aims to offer easy to use and meaningful privacy-friendly web analytics as an alternative to Google Analytics or Matomo.
Instant.Page is a JavaScript library which uses just-in-time preloading technique to make websites faster.
OpenResty is a web platform based on nginx which can run Lua scripts using its LuaJIT engine.