Two-tier Architecture A two-tier architecture corresponds to a basic client-server architecture. A two-tier architecture allows a client-side application to communicate directly with a server-side database. For example, the Railway Reservation System, Contact Management System, etc. These are common examples of two-tier architecture. Three-tier Architecture: A three-tier architecture includes an additional layer between the client and server. The introduction of the 3-tier architecture is for ease of use as it makes the system secure and provides a GUI that makes it more accessible. In this architecture, client-side applications interact with applications on the server, which in turn communicate with the database system. For example, Registration Form Designing which includes text-box, label, button or a website from internet, etc. This is one of the most frequently asked database interview questions.