AuraTech can help pick the right architecture for your solution.
We have years of experience building multi-tier solutions. We believe in n-Tier architecture because it allows applications to be re-usable and flexible. Each Tier is designed to be independent. By breaking up an application into tiers, developers only have to modify or add a specific layer if they decide to change technologies or scale up.

The figure below highlights how the Tiers are stacked.

Presentation Tier
The presentation Tier or User Interface is at the heart of Web 2.0 and Rich Internet Applications (RIA). This part of the application is built in ASP.net by developers working closely with graphic artists. Cascading Style Sheets (CSS) are used extensively to provide a consistent user experience. AJAX is used to provide continuity and a near desktop application experience. We also have experience using third party user interface controls from vendors like Telerik, Infragistics, ComponentArt, etc.
Tools We Use: ASP.net, AJAX, CSS, Silverlight, Flash, Toolkits from Telerik RadControls, Infragistics and ComponentArt.

Access Tier
Enterprise class applications often provide programmatic access to their application. This can be in the form of an API or a Web Service. AuraTech has extensive experience developing Web Services. Microsoft Web Services Enhancements can be used to secure web services.
Tools We Use: Web Services, Microsoft WSE (Web Services Enhancements)

Business Logic Tier
This really is the brain of the application. Extensive use of object oriented programming (OOP) is made to define business objects. Business processes are defined by rules of interaction between these objects. This layer is not concerned with whether business objects are stored in a database, file or session. This layer could simultaneously be used by multiple presentation/access layers written as a web interface, windows form interface or a web service.
Tools We Use: UML diagrams, OOP, C#, Visual Basic

Data Access Tier
This tier provides the logic for persisting business objects. It is responsible for mapping business objects to database tables. It handles operations such as connecting to databases, executing operations as transactions and connection pooling. Various automated tools or libraries can be used to auto-generate this layer. Using these tools can accelerate the development process and allow our developers to focus on key business processes in the Business Logic Tier. These tools also generate consistent, efficient and bug free code.
Tools We Use: NHibernate, Code Smith (net-tier), DLINQ/LINQ, Data Application Block, UML diagrams, C# and Visual Basic

Data Storage Tier
This tier's only responsibility is storage and retrieval of data. It typically consists of a Relational Database Management System (RDMS). Generic CRUD Stored Procedures can be generated by the tools used to generate the Data Access Tier. Our developers write more advanced Stored Procedures that need optimization.
Tools We Use: SQL Server, Oracle, MySQL and PostgreSQL