ORMs are great for Rapid Application Development. You can get started very quickly. The price you pay is the vast complexity they hide under the hood. As your system grows, that complexity can bite you if you are not careful enough. What is more, ORM packages create heavy objects that can make your life hard when doing batch processing. It is a great blessing to know the basic principles and challenges when persisting an object to a relational database. This knowledge will help you make some critical decisions as your application grows. by Alexandros Gougousis