Multitier

Multitier refers to software architecture that divides an application into distinct layers, or tiers, each with specific responsibilities. The most common configuration is three-tier architecture, comprising a presentation tier (user interface), an application or logic tier (business rules and processing), and a data tier (database and data storage). In a multitier design, tiers often run on separate physical or virtual servers and communicate over a network, allowing independent scaling and deployment.

The presentation tier handles user interaction, the logic tier implements business rules and workflows, and the data tier manages data storage and retrieval. Additional tiers may include integration or service tiers (to connect with external systems), caching tiers, and security or mediation layers. The architecture is described as N-tier when more than three tiers are involved.

Benefits include improved scalability, as each tier can be scaled independently; maintainability and reuse through separation of concerns; the ability to change or replace technologies in one tier without affecting others; and enhanced security boundaries, since each tier can enforce distinct policies.

Challenges include added complexity in deployment and operation, higher latency due to inter-tier communication, debugging across boundaries, and greater need for robust error handling and transaction management. In practice, multitier designs are common in web-based enterprise applications, where a browser presents the UI, a middle tier runs application logic, and a database stores data. They have historically evolved with web services and, more recently, microservices patterns that still rely on tiered separation to some extent.