What is Monolithic Architecture? How is it structured and how does it work?

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IT Interview Practice · Accepted Answer

## What is Monolithic Architecture?

**Monolithic Architecture** is a software architecture in which features are built into one unified application. The whole application is packaged and deployed together whenever a new version is released.

For example, a shopping application can include sign-in, product management, a shopping cart and orders. The code for each feature can still be organized into separate modules to make it easier to maintain.

## How is a monolithic application structured?

A traditional monolithic web application typically has three parts:

- **User interface:** Displays web pages and receives user actions, such as viewing products or submitting an order.
- **Business logic:** Handles application rules, such as validating orders, calculating totals and applying discount codes.
- **Data access:** Reads and writes information in a database, such as fetching product lists or saving orders.

These parts belong to the same application. The database stores the information and can run on a separate server.

## How does it work?

When a user sends a request, the application receives it, performs the business operations, reads or writes data and returns a result. Server-side features work together through calls within the same program.

**Example: an online shop.** When a customer places an order, the order module gets information from the product module, calculates the total and saves the order in the database. It returns a result so the interface can show the customer a confirmation. The features involved all belong to the same shopping application.

If the team changes how discount codes are applied, it releases a new version of the whole application containing that change.

## Advantages

- **Easy to get started:** The team can focus on building features in one application, with less work coordinating separate services.
- **Straightforward deployment:** Features are released together, making the process of deploying a new version easier to manage in the early stages.
- **Easier to follow the processing flow:** Testing and debugging are often more straightforward when related features run in the same application.

## Limitations

- **Harder to scale individual features:** If reporting needs more resources, adding replicas usually means running more copies of the entire application.
- **Changes can affect several parts:** When modules depend heavily on each other, changing one feature can introduce errors in another.
- **Releases can take longer:** As the codebase and test suite grow, packaging, testing and deploying the whole application can take longer.

## When should you use Monolithic Architecture?

Monolithic Architecture is a good fit when the benefits of shared development and operations outweigh the need to separate individual features:

- **New products or prototypes:** The team needs a usable version quickly to test an idea.
- **Small teams:** One team owns the features and can coordinate shared releases.
- **Applications with a clear scope:** Examples include internal HR or order-management systems that do not yet need independently deployed parts.

What is Monolithic Architecture?

How is a monolithic application structured?

How does it work?

Advantages

Limitations

When should you use Monolithic Architecture?

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