We are developing a multi-tier architecture web applications

In software engineering, multi-tier architecture or multilayered architecture is a client-server architecture in which presentation, application processing, and data management functions are physically separated. Some of the benefits of an N-layered architecture:

• Other applications will be able to reuse the functionality exposed by your layers. This is very important because of more needs for integrating multiple applications (web and mobile) into one information system.
• Having your application not layered means that you have to deal with all security threats in one place which is very difficult. Having your application distributed to layers makes it much easier for design and implement security.
• You will be able to distribute your layers over multiple physical tiers. This can make a very good impact on your application by improving performance (sometimes), scalability and fault tolerance.
• The maintenance of your application is easier because of the low coupling between layers.
• Adding more functionality to your application is made easier.
• Layers make your application more testable.
• Building well-formed layers make the orientation in your application easier.