It has a long book title but it is worth reading for those who are thinking about scaling their own website and small business growth. 'Building Scalable Web Sites: Building, Scaling, and Optimizing the Next Generation of Web Applications' which was released back in 2006, is still a great book for beginners who are looking for a basic book that can give them a run down of the basics when it comes to database scaling.
There is not much information out there on the internet at the moment, making this book more valuable for those who are serious about scaling their website. Cal Henderson, who is the author of the book, writes about his personal experience and knowledge in the area. The book goes through a number of topics in chapters that are outlined very clearly. You can get a sneak peak of the content on Amazon here.