Recently I had an ML system design interview and while I am waiting for the results I want to share the resources I found very helpful for my preparation:
Facebook Field Guide to ML. This is a very important resource to internalize, it is concise yet quite deep and full of non-trivial examples and concepts.
"The hundred-page Machine Learning book" by Andriy Burkov. A perfect book in case you want to refresh your core ML knowledge.
Google crash ML course. This course is also great to solidify your knowledge of fundamental ML principles with the full-scale industrial projects in mind.
Two installments of ML systems from UC Berkeley. The videos are not available, unfortunately; but you can look thought the syllabus and study the readings required for the course:
Good luck!