How to undo on keyboard using shortcuts?

I'm a graphic designer working on a tight deadline, and I've just realized that I accidentally made some design changes in Adobe Photoshop that I need to revert back to. I know there are plenty of tutorials online about how to use the 'Undo' feature, but I could really use a quick reminder on how to do it using keyboard shortcuts specifically. Does anyone have any tips or tricks for undoing actions quickly without having to go through the menu every time? Any help would be greatly appreciated!