Design for scalability

If you develop large J2EE or WEB application using Java you should always think about scalability of your application (of course if you expect your application to be popular). Nobody tell you that you should scale your application initially, but take in mind that some architecture solutions may make it really hard to scale in the future. You have two common approaches: vertical and horizontal scalability. Both approaches has their requirements for code base to be applied effectively. I have found very interesting article on the www.theserverside.com about J2EE scalability written by Wang Yu from of Sun Microsystems. Article contains two parts: vertical and horizontal scalability. Take this information in mind when make architectural decisions. Develop with pleasure!