A 1.2 GB image for a service that's a few megabytes of compiled code is one of those things everyone accepts until someone actually looks at it. Slow pulls, slow deploys, a bigger attack surface, and a registry bill that creeps up quietly. The good news is that bloated images are almost always the result of a handful of specific, fixable habits — not some deep property of Docker.
I want to walk through how I actually slim an image down, in the order I'd do it, with a before-and-after you can map onto your own Dockerfile. Nothing here is exotic. It's mostly about not shipping things you don't need, and knowing how to see what you are shipping.
First, look before you cut
You can't slim what you can't see, so the two commands I reach for first are:
docker history myapp:1.4.2
