Is it possible to use Lua Scripting to minify css, and js on the fly?
It’s not possible because the Lua can modify only the http object that can contains entirely in one haproxy buffer.
The on-flight content modification is one of the most required feature. I’m waiting the HTTP/2 implementation for proposing a way to modify the objects content.
So, you can minify CSS and JS that contains in one HAProxy buffer.