The stale Excel export was Cloudflare, not Excel

I edited some data in an app I maintain, downloaded the Excel export again, and the file showed the state before my edit. On another machine the same download showed the current state. My first suspect was the change I had made to downloads the day before, when Safari refused to save a file. It wasn’t that. The problem predates it. Same URL, same edge, same file The app sits behind Cloudflare. None of its 17 export routes sent a Cache-Control header, which I had never thought about because every one of them requires a login.