What breaks in production — and what developers use instead It usually starts with a simple requirement. "Upload an Excel file, process it on the server, and export a report." So you reach for Microsoft.Office.Interop.Excel . It's familiar. It's part of the Microsoft ecosystem. And it works — at least on your machine. You open a workbook. You read a few cells. You write a test. Everything passes. Then you deploy to production. Within days, you start noticing things: Excel processes quietly pile up in Task Manager, never exiting Some requests hang indefinitely with no error, no timeout, no explanation IIS recycles unexpectedly under moderate load A background job that worked fine in staging fails intermittently Deploying to a new server means installing Microsoft Office — and hoping the license key is somewhere None of these failures are dramatic at first. They're subtle. They show up gradually. And by the time the pattern is obvious, they're already embedded in production infrastructure.…