A 3-tier application architecture is a modular client-server
architecture that consists of a presentation tier, an application tier and a
data tier. The data tier stores information, the application tier handles logic
and the presentation tier is a graphical user interface (GUI) that communicates
with the other two tiers. The three tiers are logical, not physical, and may or
may not run on the same physical server.
- Presentation tier - This tier, which is built with HTML5, JavaScript and
cascading style sheets (CSS), is deployed to a computing device through a web
browser or a web-based application. The presentation tier communicates with the
other tiers through application program interface (API) calls.
- Application tier - The application tier, which may also be referred to
as the logic tier, is written in a programming language such as Java, Python or
Ruby and contains the business logic that supports the application's core
functions. The underlying application tier can either be hosted on distributed
servers in the cloud or on a dedicated in-house server, depending on how much
processing power the application requires.
- Data tier - The data tier consists of a database and a program
for managing read and write access to the database. This tier may also be
referred to as the storage tier and can be hosted on-premises or in the cloud.
Popular database systems for managing read/write access include MySQL, Oracle,
PostgreSQL, Microsoft SQL Server and MongoDB.
The benefits of using a 3-layer architecture include improved scalability, performance and availability. With three tiers or parts, each part can be developed concurrently by a different team of programmers coding in different languages from the other tier developers. Because the programming for a tier can be changed or relocated without affecting the other tiers, the 3-tier model makes it easier for an enterprise or software packager to continually evolve an application as new needs and opportunities arise. Existing applications or critical parts can be permanently or temporarily retained and encapsulated within the new tier of which it becomes a component.
3-tier application programs may also be referred to as n-tier programs. In
this context, the letter "n" stands for 'a number of tiers.'
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