Traditional Monolithic vs 3-Tier Architectures

When it comes to building and deploying software, there are a variety of architectural patterns to choose from. One popular option is the 3-tier architecture, which is a variation of the traditional monolithic architecture. In this post, we'll discuss the two architectures, highlighting their pros and cons, and examine a real-world example of how a company can leveraged the power of Amazon Web Services (AWS) to implement a 3-tier architecture.

Traditional Monolithic Architecture

The monolithic architecture has been a popular choice for many years when it comes to building and deploying software. This approach involves creating a single, large codebase that handles all the functionality for a given application as illustrated in fig.1 below. The presentation layer, Data tier, and Database are all piled up in a single server. However, as the world of cloud computing and distributed systems has evolved, the monolithic architecture has come under scrutiny for its potential limitations. Below are some of the pros and cons for the Traditional Monolithic Architecture.

Pros of Monolithic Architecture

ü?Easy to understand and develop: Since all the functionality is contained within a single codebase.

ü?It's relatively easy for developers to understand how the application works and make changes as needed.

ü?Simple deployment: With a monolithic architecture, there's no need to worry about coordinating multiple codebases or services; all you need to do is deploy the single codebase to your servers.

Cons of Monolithic Architecture

1. ?Limited scalability: As the application grows and its user base increases, it can become difficult to scale a monolithic codebase to handle the increased load. This can lead to poor performance and frustrated users.
2. ?Difficulty in separating concerns: A monolithic codebase can become difficult to manage and test as it grows, making it harder to separate concerns such as user management, data storage, and business logic. This can lead to a lack of modularity and reusability in the code.
3. ?Lack of flexibility: A monolithic architecture can make it difficult to make changes to certain parts of the application without affecting the entire codebase. This can lead to delays in releasing new features or updates.
4. ?Difficulty in implementing microservices: With a monolithic architecture, it can be difficult to break down the application into smaller, more manageable services. This can make it harder to take advantage of the benefits of microservices such as improved scalability and fault isolation.
5. ?Difficulty in deploying and testing: In a monolithic architecture, deploying and testing the entire application can be time-consuming and complex. This can lead to longer lead times for releases and more difficulty in identifying and resolving bugs.

Three-Tier Architecture

A “3-tier” architecture is a common software architecture pattern that separates the application into three distinct layers or tiers:

1. Presentation (Web Tier)
2. Middle Tier (Application Tier)
3. ?Data Tier

The first tier, also known as the Presentation tier, is responsible for handling the user interface and presentation logic. This is what is commonly referred to as the Web Tier. It is the part of the application that interacts directly with the user and is responsible for handling the user's requests and providing a response. It’s typically implemented as a set of web pages or web services that can be accessed via a web browser or a mobile application. The web tier can include a variety of technologies such as HTML, CSS, JavaScript and front-end frameworks such as React, Angular, Vue.js and more. The web tier also handles security, authentication and authorization, it manages the session and cookies.

The Middle Tier also known as Application Tier, is responsible for implementing the business logic of the system and processing requests from the presentation tier. The application tier acts as an intermediary between the presentation tier and the data tier, handling the communication between them. It receives requests from the presentation tier, processes them according to the business logic, and then communicates with the data tier to retrieve or update the necessary data. The application tier also performs any necessary validation and error handling. The application tier is typically implemented using a server-side programming language such as Java, C#, or Python, and can include a variety of different technologies such as web frameworks, application servers, and middleware.

In a 3-tier architecture, the Data Tier is responsible for storing and managing the data used by the other tiers. It is typically implemented using a database management system (DBMS) and can include a variety of different types of databases, such as relational databases, document databases, and key-value stores. In AWS, there are several services that can be used to implement the data tier:

Amazon RDS: This service allows you to easily set up, operate, and scale a relational database in the cloud. It supports several popular relational database engines such as MySQL, PostgreSQL, Aurora, MS SQL and Oracle.

Amazon DynamoDB: This service is a fully managed NoSQL database service that supports key-value and document data models. It provides fast and predictable performance with seamless scalability.

Amazon DocumentDB: a fully managed document database service that supports MongoDB workloads. It is designed to be compatible with your existing MongoDB applications and tools.

Amazon Elasticsearch Service: This service makes it easy to deploy, operate, and scale Elasticsearch clusters in the cloud. Elasticsearch is a popular open-source search and analytics engine.

These services can be used to store and manage a wide variety of data, such as user information, product catalogs, and log data. They provide a range of features to support the scalability, availability, and security of the data tier.

Additionally, AWS provides services like AWS Glue, AWS Data Pipeline and AWS Lake Formation that can be used to manage, clean and process the data in the data-tier, making it ready for consumption by the application-tier.

Having discussed the three layers in detailed let us now dive deep into Pros and Cons of a Three Tier Architecture.

Pros of a Three-Tier Architecture

Scalability: In a three-tier architecture, the different tiers can be scaled independently, allowing for better resource allocation and improved performance. This means that if one tier becomes a bottleneck, it can be scaled up without affecting the other tiers. For example, if the application needs to handle a large number of concurrent users, the web server tier can be scaled horizontally by adding more servers, without affecting the database or application logic tiers.

Modularity: A three-tier architecture allows for greater modularity and separation of concerns, making it easier to add new functionality or make changes to existing functionality without affecting the entire system. Each tier has a specific purpose, so changes to one tier do not require changes to the other tiers. This results in a more maintainable and flexible system.

Reusability: The separation of concerns in a three-tier architecture allows for greater code reuse, as different layers can be reused in different parts of the system. For example, the business logic tier can be reused in different applications, or the data access tier can be reused to connect to different databases.

Flexibility: A three-tier architecture allows for different technologies to be used for different layers, giving developers more flexibility in choosing the tools and technologies that best suit the requirements of the system. For example, a Java EE application can use a JPA for data access and a JSF for the presentation layer.

Maintainability: A three-tier architecture makes it easier to maintain and update the system, as changes can be made to individual layers without affecting the entire system. This is beneficial for large and complex systems, as it allows for more manageable and efficient development. The separation of concerns also makes it easier to identify and fix bugs.

Cons

1. Increased complexity: A three-tier architecture can increase the complexity of a system, as there are more components and layers to manage and maintain. This can make it harder to understand how the system works and to troubleshoot issues.
2. ?Higher cost of development and maintenance: Because of the added complexity, development and maintenance costs for a three-tier system can be higher than for a monolithic system.
3. ?Additional infrastructure: A three-tier architecture requires additional infrastructure, such as load balancers, to manage the different tiers and ensure that they are working together properly.

Scenario

?A real-world scenario where a three-tier architecture would be more preferred to a monolithic architecture is in the development of a large e-commerce platform.

An e-commerce platform typically has a large number of concurrent users and needs to handle a high volume of transactions. A monolithic architecture may not be able to handle this level of traffic and scalability efficiently.

A three-tier architecture, on the other hand, allows for the separation of concerns and better resource allocation. The presentation layer, which handles the user interface, can be scaled horizontally to handle a large number of concurrent users. The application logic layer, which handles the business logic, can also be scaled separately to handle the high volume of transactions. The data access layer, which handles the database, can be optimized, and scaled to handle the large amount of data.

Additionally, the separation of concerns in a three-tier architecture allows for greater modularity and code reuse. The business logic layer can be reused in different parts of the system, and new functionality can be added to the presentation layer without affecting the rest of the system. This makes it easier to maintain and update the system as illustrated in the diagram below.

In conclusion, both three-tier and monolithic architectures have their own advantages and disadvantages. A three-tier architecture allows for better scalability, modularity, reusability, flexibility, and maintainability, making it well suited for large and complex systems. However, it can also increase the complexity and cost of development and maintenance and may have increased latency due to the additional network communication between the tiers. On the other hand, a monolithic architecture is simpler to develop and maintain, but may not be able to handle large and complex systems and may not have the same level of scalability as a three-tier architecture. The choice between a three-tier and monolithic architecture will depend on the specific requirements of the system and the goals of the development team.