ZweiTier

zweiTier is a term used in information technology to refer to a two-tier client–server architecture. In this pattern, the presentation and sometimes portions of the business logic run on the client, while the data layer is hosted on a server. The term is common in German-language IT literature and is often contrasted with three-tier or multi-tier architectures, where a separate application server provides an additional processing layer between the client and the data store.

In a typical zweiTier setup, the client communicates directly with the database server across a network. This arrangement reduces the number of architectural layers and can simplify development and deployment, especially for small and medium-sized deployments. However, it can lead to tighter coupling between the user interface and data, increased bandwidth for large data transfers, and security risks from direct database exposure.

Advantages include lower complexity, faster development for simple scenarios, and potentially lower hardware costs. Limitations include reduced scalability, harder maintenance as both UI and data models evolve, and more challenging security and access control in larger organizations.

Common use cases are legacy business applications and small to mid-sized deployments where a quick-to-deploy solution is desired. For larger systems or web-based applications, three-tier or multi-tier architectures are often preferred to improve scalability, security, and maintainability.