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In software engineering, a software design pattern (also known as a software architecture pattern) is a generally applicable and reusable solution to a frequently occurring problem within a given context in software design. It is not a finished solution that can be transformed directly into code that will solve the business problem but a template that describes how to solve a problem that is applicable in several situations.

There are formalized best practices that one can use to solve common problems when writing an application. These best practices are created by trial and error by numerous software developers over quite a substantial period of time. One often ends up in software engineering solving problems that are similar to each other. Using design patterns reduces the necessity to find and implement the solution each time a new problem is encountered.

Model View Controller (MVC) architecture is one of the most famous design patterns in the field of modern software engineering. We can describe the MVC architecture by its three main components:

Model: This is the central component of the design pattern. It is the application’s dynamically defined data structure that is defined as per the needs of the problem. It is directly responsible for managing the data, for example, it is the part of the application that deals with the database and any other functionality required by the database.
View: View is the representation of information that is visible to the user. It can be the pages that we send to the client or the diagrams that represent data, such as a bar chart.
Controller: This contains the main logic of our application and the interface between models and views. It interprets and sends commands to either the view or the controller. We can call the models to fetch data or use views to show information to the users.

According to the acclaimed book “Design Patterns: Elements of Reusable Object-Oriented Software” written by the “Gang of Four”, the two key benefits of MVC are that it allows you to:

attach multiple views to a model to provide different presentations (view/model decoupling)
change the way a view responds to user input without changing its visual presentation (view/controller decoupling)

The MVC Pattern has had many other design patterns inspired by it such as MVVC, MV-Adapter, and MV-Presenter. MVCS (MVC + Service Layer) is another such design pattern that has entered the arena but doesn’t have much literature around it. This article provides a detailed introduction to this architecture.

MVCS architecture

MVCS is different from MVC in a few ways that makes it unique. The standard architecture of MVCS is as follows:

Middleware layer: Responsible only for modifying or managing a group of controller actions
Controller layer: Responsible only for receiving the request and displaying the result of the operation
Service Layer: Also known as the Business Layer, contains the functionality that compounds the core of the application, thus becoming highly reusable for controllers and services
Model Layer: Responsible for defining how is defined the data model
View Layer: Represents how the data will be rendered to the view

The main benefits of this approach are:

Business applications typically require different kinds of interfaces to the stored data and the logic they implement. They, however, need interfaces to interact with the application to access and work on the data and invoke business logic of the company. Encoding the logic of the interactions separately in each interface causes a lot of duplication. MVCS helps reduce this issue.
Framework-agnosticism reduces time and effort in upgrading the applications. The Service Layer is developed “away” from the framework being used (e.g., Flask), so upgrading or replacing it is trivial.
Predictable development and testing patterns create a common language for developing and testing different responsibilities. Abstracting persistence allows for test fixtures that don’t need to interact with a database.
Collaborative language moves the conversation away from how to develop and test commonly recurring functionality, to how to organize responsibilities and how different layers of an application should interact.

As applications continue to become complex with time, it becomes imperative to keep codes and programs structured in a uniform format that ensures security and makes collaboration easier. With MVCS architecture, you can save on time and cost by creating applications faster and easier while keeping them secure.

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