I've been massively recommending this book. I think it's very unlikely a backend engineer can avoid having their applications on multiple servers. This book does a wonderfully clear and practical description of the issues with distributed systems, and tools and techniques to address those issues. It's written in a way that is very accessible to someone without a traditional comp sci background.

I was excited about this book because there is a gap in distributed systems books. I feel like there's are a large amount of blogs but most of the books available on amazon are text books and/or include heavy math.