Monolithic applications have been the traditional way of building software systems. In a monolithic application, all the code and functionality are packaged into a single executable or codebase. The architecture of a monolithic application typically consists of three layers: presentation, application, and data storage.

In the presentation layer, the user interface (UI) is designed, and the user interacts with the application. The application layer contains the business logic of the application, and the data storage layer is responsible for storing the data.

One of the significant advantages of a monolithic application is its simplicity. Since everything is packaged in a single executable, it is easy to deploy and manage. Additionally, it is straightforward to develop as all the functionality is in one place. This also makes it easier to maintain as there are no external dependencies to manage.

However, as applications become more complex, the monolithic architecture starts to show its limitations. As the application grows, it becomes harder to manage, and the codebase becomes harder to understand. It also becomes difficult to scale the application, both in terms of performance and development. Adding new features can be time-consuming and costly as it requires changing the entire codebase.

Moreover, a monolithic application is also more prone to failure since a problem in one part of the application can cause the entire application to fail. It can also be difficult to adopt new technologies as the entire codebase must be updated.

As a result, many companies are moving away from the monolithic architecture and adopting a more modern approach, such as microservices architecture. In a microservices architecture, the application is broken down into smaller, independent services that can be developed, deployed, and scaled independently. This approach allows for greater flexibility, scalability, and resilience.

In conclusion, while monolithic applications have been the traditional way of building software systems, they have their limitations. As applications become more complex, it becomes harder to manage, scale and maintain a monolithic application. Therefore, modern approaches like microservices architecture are gaining popularity, providing more flexibility, scalability, and resilience.