My Time Machine backups started taking an insane amount of time to complete. After some research, I was able to determine that it was caused by all of my NPM modules I had installed for various projects.
I found this fabulous tool that periodically scans your codebases and adds ignore rules to Time Machine for you: https://github.com/stevegrunwell/asimov
I installed this using
brew install asimov
and then enabled it:
sudo brew services start asimov