Using a special software for database modeling, we prepare not only map for the development of database but also documentation for Client.
Documentation (diagrams and schemes) can explain to you any mechanism's function.
It is not a necessary stage of development but very comfortable for futher working with the product.
The backend part of a server is the main part that determine logical and functionality needs of a server.
We think that it is main part just because design changes periodically with the help of design patterns or designer, but logic will be the same far a long time.