In which application model do servers and databases exist in multiple locations?

The N-tier application model is characterized by its architecture that separates different functions into distinct layers or tiers. In this model, servers and databases can exist in multiple locations, allowing for a more scalable and flexible system. This separation of concerns enables the application to distribute its processes across different servers, which can reside in various locations, enhancing performance and reliability.

For instance, in an N-tier architecture, you could have a presentation layer that runs on client devices, a business logic layer hosted on a separate server, and a data access layer that interacts with databases potentially situated in cloud environments or on-premises systems at different sites. This distribution improves resource management and can enhance security since each tier can be secured independently.

In contrast, the other models like two tier, one tier, and single tier do not provide the same level of distribution. The two-tier model typically connects a client directly to a database server, which limits the locations of the servers. The one-tier model is a more simplified structure where everything is integrated into a single platform. The single tier model refers to a scenario where both the server and the client reside on the same machine, meaning all components are centralized and not distributed across multiple locations. Hence, the N-tier model is the most suitable choice