Two Packages, Four Scripts, One 2 GB Server: Building an Upload Pipeline That Never Double-Posts I still remember the night I found out I had posted the same 14 vectors twice. It was 1 a.m. I had run my batch, saw it finish, changed one keyword, and ran it again. Two days later I got a polite email from a marketplace asking me to explain the duplicates. That email cost me a week of cleaning up, and it taught me something that shaped every script I have written since: the pipeline must kno...