Your Docker Builds Are Slow Because You're Doing It Wrong (And I Built a Tool to Prove It)

Stop waiting 10 minutes for CI to rebuild everything when you change one line of code. Here's what's actually breaking your Docker layer cache."

This post is about Docker layer caching and why your builds probably take way longer than they should. If you've ever sat there watching Docker reinstall npm packages for the 10th time today after changing one line, yeah this is for you.

The Pain

Okay so. You know that feeling, right? You changed literally ONE line of code. Fixed a typo in a comment or whatever. Push it up, CI kicks off, and now you're sitting there watching Docker reinstall 400 npm packages. Again. For the third time today.

And you're like "why is this happening to me"