Past winter, I had to deploy a new version of a package that was used by a lot of our applications (at least 5 apps, some for our customers, and some internal ones).

Because it was a "simple" package, we did not have any deployment system ready, and deploying was just SSH/SCP commands that created a directory with the package version and upload my dist. I forgot to bump the package version, and ended up wiping a working and in-use package. The problem is that this package can only work up to a specific angular version (which wasn't set in the package.json, so my build installed the wrong one), therefore the only thing that our applications were producing was a blank page.

And because I had wiped the original package, I had no way to know which angular version we needed, and we had to find a cached version to get it, by reading the angular license comment in the minified code. The shittiest 5 mins of my life, even though I'm sure no one noticed it.

What I learned from this : don't speak with someone else while deploying, huge focus loss.

PS : The company is an ISP.