I personally really like System Design in a Hurry. I think the best approach is to:
- Read the guide (the first section is “How to Use This Guide” which will let you know what to do based on how much time you have)
- Do a couple practice interviews with friends
- The difference between someone who’s done a practice interview and who hasn’t is night and day. You’ll catch and fix an insane amount of mistakes/issues in your first practice interview, absolutely do not skip this step.