Three-tier architecture is a client–server software architecture pattern in which the user interface (presentation), functional process logic ("business rules"), computer data storage and data access are developed and maintained as independent modules, most often on separate platforms.

The following are the advantages of Three-Tier systems:

Clear separation of user-interface-control and data presentation from application-logic:

With the help of this separation, more clients are able to have access to a wide variety of server applications. The two main advantages for client-applications are quicker development through the reuse of pre-built business-logic components and a shorter test phase.

Dynamic load balancing:

If bottlenecks in terms of performance occur, the server process can be moved to other servers at runtime.

Change management:

It is easy and faster to exchange a component on the server than to furnish numerous PCs with new program versions.

The disadvantages of Three-Tier systems are as below:

• It creates an increased need for network traffic management, server load balancing, and fault tolerance.
• Current tools are relatively immature and are more complex.
• Maintenance tools are currently inadequate for maintaining server libraries.