From 10+ years ago when I worked at PayPay, webscr (the frontend at the time, where you'd log in) was a total of 2GB of C++ that would get compiled into a 1GB CGI executable, deployed over some ~700+ web servers.

Debug versions would never get compiled, as I'm told the resulting file was too large for the filesystem to handle.

Apparently a great deal of the code was actually inline XML.

They knew this was a bad pile of technical debt, too: at one point, a senior/staff engineer gave a company presentation where they brought a fanfold printout of the main header file for this monstrosity, and literally unrolled it across the entire stage.