Applying 3-Tier Architecture to Organize Apps’ Code

Sometimes applications have messy codebase. It happens. You’ll need time to determine where particular features are located and it can be a challenge for unit tests, debugging, or adding new functionality.

However, 3-tier architecture (that is sometimes called three-layer architecture) is a real solution. In case you are striving to deliver an outstanding software product and your customers, then the 3-tier architecture is a beneficial choice that you really need. It provides programmers with an opportunity to modularize and configure their applications in the most proper way.

In this post, we will briefly describe the essence, benefits, and possible drawbacks of the 3-layer architecture.

What is 3-Tier Architecture?

Three-tier is a client-server architecture where you develop and maintain the UI, functional process logic, computer data storage, and data access – all as independent modules. Most often they are developed on separate platforms.

This model is a software architecture pattern. It provides typical advantages of modular software with well-defined interfaces. Besides, the 3-tier architecture is intended to allow any of tiers to be upgraded or replaced independently in response to changes.

This kind of architecture has three tiers:

1. Presentation tier

This is the topmost application level that displays information related to browsing merchandise, purchasing and shopping cart contents. The presentation tier communicates with other tiers by outputting results to the browser or client tier and all other tiers in the network.

2. Logical tier

Logical (application) tier presents business logic, logic tier, data access tier, or middle tier. The tier is pulled out from the presentation tier and, as its own layer, it controls an app’s functionality by performing detailed processing.

3. Data tier

Data tier includes database servers. The information is stored and retrieved here. It keeps data independent from app servers or business logic. It influences scalability and performance.

What are the rules the 3-Tier architecture requires?

1. The main rule sounds like “the presentation layer is only a shell. I cannot contain any processing of BizLogic”.
2. The design should form the app layer rather than presentation one. The API of the application layer should implement all BizLogic on the API in an object-oriented manner.
3. Take care of the data layer that should be independent of the abstract system layer.
4. You may apply an enterprise service or a remote object technology, you may also deploy it on a server or not, but you must consider clustering multiple servers through load balancing in your design.

Pros of Using a 3-Tier Architecture

• The 3-tier architecture decreases dependencies between layers.
• As long as use the same entity classes of the object model and follow the interface standards, it lets developers work on every layer, that may essentially improve the development speed of the system.
• The layers can be modernized or redeveloped with no affecting other layers in a 3-tier architecture. That is why the time to market shortens and the cost to integrate new features into SaaS and on-premises apps reduce.
• 3-tier architecture provides ease of maintenance. It significantly reduces maintenance time and costs.
• Every part can be developed concurrently by different programmers that code in different programming languages from the other tier developers.

Are There Any Cons?

• The 3-tier architecture negatively affects system performance. Businesses could go directly to the database to get the data without a hierarchical structure. However, now they have to go through the middle tier.
• Sometimes it results in cascading changes. Especially in the top-down direction. In case you need to add a feature into the presentation tier, you may need to add code in both the business logic layer and the data access layer to ensure that the design is layered.

Two-tier vs three-tier architectures: what is the difference?

The added modularity is what initially differ a 3-tier application over a 2-tier application. It actually allows the replacement of any layer without affecting other ones and separating business functions from database-related functions. The 3-layer system is also about advanced flexibility, reusability, scalability, manageability, and maintainability.

Is 3-tier architecture the same as MVC?

Some people consider the MVC (Model-View-Controller) design pattern identically to the 3-tier architecture.

• It is true but only to some extent. Here are the vivid differences between both models:
• The View and Controller fit into the Presentation layer. There is no separate component for data access in the MVC. However, the Model and Business tiers seem identical.

Wrap up

The 3-tier architecture is much more than academic exercising with essential costs and some limited benefits. In comparison with the MVC design pattern, it has a more streamlined separation of responsibilities.

The three-tier architecture allows involving different teams with multiple skills to develop each layer. It can provide multiple data access objects at the same time. It also gives a chance to build front-end sites consisting of nothing more than an additional presentation layer.

What do you think about the use of the 3-tier architecture? Please, share your experience and thoughts.