In a past life the most “fun” I had as a developer on a CAD file processing solution was discovering that engineers loved linking Excel sheets to the CAD files so crucial calculations could be done there. And then having to make this work on Linux servers.
I had to run a very large accounting Excel file inside a web service about ten years ago. The service was born as manually operated Excel sheet plus interaction by email/phone and they wanted to scale it on the web.
I run it on Windows Server and paid somebody to write the Windows service to manage the Excel sheet. I can't remember which language I used for the web service itself.
They eventually gave up, commercial problems, not technical ones.
