what is a presentation tier architecture

Three-tier architecture is a well-established software application architecture that organizes applications into three logical and physical computing tiers: the presentation tier, or user interface; the application tier, where data is processed; and the data tier, where application data is stored and managed.

The chief benefit of three-tier architecture is that because each tier runs on its own infrastructure, each tier can be developed simultaneously by a separate development team. And can be updated or scaled as needed without impacting the other tiers.

For decades three-tier architecture was the prevailing architecture for client-server applications. Today, most three-tier applications are targets for modernization that uses cloud-native technologies such as containers and microservices and for migration to the cloud.

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Presentation tier

The presentation tier is the user interface and communication layer of the application, where the end user interacts with the application. Its main purpose is to display information to and collect information from the user. This top-level tier can run on a web browser, as desktop application, or a graphical user interface (GUI), for example. Web presentation tiers are developed by using HTML, CSS, and JavaScript. Desktop applications can be written in various languages depending on the platform.

Application tier

The application tier, also known as the logic tier or middle tier, is the heart of the application. In this tier, information that is collected in the presentation tier is processed - sometimes against other information in the data tier - using business logic, a specific set of business rules. The application tier can also add, delete, or modify data in the data tier. 

The application tier is typically developed by using Python, Java, Perl, PHP or Ruby, and communicates with the data tier by using  API  calls. 

The data tier, sometimes called database tier, data access tier or back-end, is where the information that is processed by the application is stored and managed. This can be a  relational database management system  such as  PostgreSQL , MySQL, MariaDB, Oracle, Db2, Informix or Microsoft SQL Server, or in a  NoSQL  Database server such as Cassandra,  CouchDB , or  MongoDB . 

In a three-tier application, all communication goes through the application tier. The presentation tier and the data tier cannot communicate directly with one another.

Tier versus layer

In discussions of three-tier architecture,  layer  is often used interchangeably – and mistakenly – for  tier , as in 'presentation layer' or 'business logic layer'. 

They aren't the same. A 'layer' refers to a functional division of the software, but a 'tier' refers to a functional division of the software that runs on infrastructure separate from the other divisions. The Contacts app on your phone, for example, is a  three - layer  application, but a  single-tier  application, because all three layers run on your phone.

The difference is important because layers can't offer the same benefits as tiers.

Again, the chief benefit of three-tier architecture is its logical and physical separation of functionality. Each tier can run on a separate operating system and server platform - for example, web server, application server, database server - that best fits its functional requirements. And each tier runs on at least one dedicated server hardware or virtual server, so the services of each tier can be customized and optimized without impacting the other tiers. 

Other benefits (compared to single- or two-tier architecture) include:

• Faster development : Because each tier can be developed simultaneously by different teams, an organization can bring the application to market faster. And programmers can use the latest and best languages and tools for each tier.
• Improved scalability : Any tier can be scaled independently of the others as needed.
• Improved reliability : An outage in one tier is less likely to impact the availability or performance of the other tiers.
• Improved security : Because the presentation tier and data tier can't communicate directly, a well-designed application tier can function as an internal firewall, preventing SQL injections and other malicious exploits.

In web development, the tiers have different names but perform similar functions:

• The web server  is the presentation tier and provides the user interface. This is usually a web page or website, such as an ecommerce site where the user adds products to the shopping cart, adds payment details or creates an account. The content can be static or dynamic, and is developed using HTML, CSS, and JavaScript.
• The application server  corresponds to the middle tier, housing the business logic that is used to process user inputs. To continue the ecommerce example, this is the tier that queries the inventory database to return product availability, or adds details to a customer's profile. This layer often developed using Python, Ruby, or PHP and runs a framework such as Django, Rails, Symphony, or ASP.NET.
• The database server  is the data or backend tier of a web application. It runs on database management software, such as MySQL, Oracle, DB2, or PostgreSQL.

While three-tier architecture is easily the most widely adopted multitier application architecture, there are others that you might encounter in your work or your research.

Two-tier architecture 

Two-tier architecture is the original client-server architecture, consisting of a presentation tier and a data tier; the business logic lives in the presentation tier, the data tier or both. In two-tier architecture the presentation tier - and therefore the end user - has direct access to the data tier, and the business logic is often limited. A simple contact management application, where users can enter and retrieve contact data, is an example of a two-tier application. 

N-tier architecture

N-tier architecture - also called or multitier architecture - refers to  any  application architecture with more than one tier. But applications with more than three layers are rare because extra layers offer few benefits and can make the application slower, harder to manage and more expensive to run. As a result, n-tier architecture and multitier architecture are usually synonyms for three-tier architecture.

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Understanding the architecture of a 3-tier application

Michael Chiaramonte

May 13, 2024

In software development, it’s very common to see applications built with a specific architectural paradigm in mind. One of the most prevalent patterns seen in modern software architecture is the 3-tier (or three-tier) architecture. This model structures an application into three distinct tiers: presentation (user interface), logic(business logic), and data (data storage).

The fundamental advantage of 3-tier architecture lies in the clear separation of concerns. Each tier operates independently, allowing developers to focus on specific aspects of the application without affecting other layers. This enhances maintainability, as updates or changes can be made to a single tier with minimal impact on the others. 3-tier applications are also highly scalable since each tier can be scaled horizontally or vertically to handle increased demand as usage grows.

This post delves into the fundamentals of 3-tier applications. In it, We’ll cover:

• The concept of 3-tier architecture: What it is and why it’s important.
• The role of each tier: Detailed explanations of the presentation, application, and data tiers.
• How the three tiers interact: The flow of data and communication within a 3-tier application.
• Real-world examples: Practical illustrations of how 3-tier architecture is used.
• Benefits of this approach: Advantages for developers, architects, and end-users.

With the agenda set, let’s precisely define the three tiers of the architecture in greater detail.

What is a 3-tier application?

A 3-tier application is a model that divides an application into three interconnected layers:

• Presentation Tier: The user interface where the end-user interacts with the system (e.g., a web browser or a mobile app).
• Logic Tier: The middle tier of the architecture, also known as the logic tier, handles the application’s core processing, business rules, and calculations.
• Data Tier: Manages the storage, retrieval, and manipulation of the application’s data, typically utilizing a database.

This layered separation offers several key advantages that we will explore in more depth later in the post, but first, let’s examine them at a high level. 

First, it allows for scalability since each tier can be scaled independently to meet changing performance demands. Second, 3-tier applications are highly flexible; tiers can be updated or replaced with newer technologies without disrupting the entire application. Third, maintainability is enhanced, as modifications to one tier often have minimal or no effect on other tiers. Finally, a layered architecture allows for improved security, as multiple layers of protection can be implemented to safeguard sensitive data and business logic.

How does a 3-tier application work?

The fundamental principle of a 3-tier application is the flow of information and requests through the tiers. Depending on the technologies you use, each layer has mechanisms that allow each part of the architecture to communicate with the other adjacent layer. Here’s a simplified breakdown:

• User Interaction: The user interacts with the presentation tier (e.g., enters data into a web form or clicks a button on a mobile app).
• Request Processing: The presentation tier sends the user’s request to the application tier.
• Business Logic: The logic tier executes the relevant business logic, processes the data, and potentially interacts with the data tier to retrieve or store information.
• Data Access: If necessary, the application tier communicates with the data tier to access the database, either reading data to be processed or writing data for storage.
• Response: The logic tier formulates a response based on the processed data and business rules and packages it into the expected format the presentation tier requires.
• Display: The presentation tier receives the response from the application tier and displays the information to the user (e.g., updates a webpage or renders a result in a mobile app).

The important part is that the user never directly interacts with the logic or data tiers. All user interactions with the application occur through the presentation tier. The same goes for each adjacent layer in the 3-tier application. For example, the presentation layer communicates with the logic layer but never directly with the data layer. To understand how this compares to other n-tier architectural styles, let’s take a look at a brief comparison.

1-tier vs 2-tier vs 3-tier applications

While 3-tier architecture is a popular and well-structured approach, it’s not the only way to build applications. As time has passed, architecture has evolved to contain more layers. Some approaches are still used, especially in legacy applications. Here’s a brief comparison of 1-tier, 2-tier, and 3-tier architectures:

• All application components (presentation, logic, and data) reside within a single program or unit.
• Simpler to develop initially, particularly for small-scale applications.
• It becomes increasingly difficult to maintain and scale as complexity grows.
• Divides the application into two parts: the client (presentation/graphical user interface) and a server, which typically handles both logic and data.
• Offers some modularity and improved scalability compared to 1-tier.
• Can still face scalability challenges for complex systems, as the server tier combines business logic and data access, potentially creating a bottleneck.
• Separates the application into presentation, application (business logic), and data tiers.
• Provides the greatest level of separation, promoting scalability, maintainability, and flexibility.
• Typically requires more development overhead compared to simpler architectures.

The choice of architecture and physical computing tiers that your architecture uses depends on your application’s size, complexity, and scalability requirements. Using a multi-tier architecture tends to be the most popular approach, whether client-server architecture or 3-tier. That being said, monolithic applications still exist and have their place.

The logical tiers of a 3-tier application architecture

The three tiers at the heart of a 3-tier architecture are not simply physical divisions; they also represent a separation in technologies used. Let’s look at each tier in closer detail:

1. Presentation tier

• Focus: User interaction and display of information.
• Role: This is the interface that users see and interact with. It gathers input, formats and sanitizes data, and displays the results returned from the other tiers.
• Web Development: HTML, CSS/SCSS/Sass, TypeScript/JavaScript, front-end frameworks (React, Angular, Vue.js), a web server.
• Mobile Development: Platform-specific technologies (Swift, Kotlin, etc.).
• Desktop Applications: Platform-specific UI libraries or third-party cross-platform development tools.

2. Logic tier

• Focus: Core functionality and business logic.
• Role: This tier is the brain of the application. It processes data, implements business rules and logic, further validates input, and coordinates interactions between the presentation and data tiers.
• Programming Languages: Java, Python, JavaScript, C#, Ruby, etc.
• Web Frameworks: Spring, Django, Ruby on Rails, etc.
• App Server/Web Server

3. Data tier

• Focus: Persistent storage and management of data.
• Role: This tier reliably stores the application’s data and handles all access requests. It protects data integrity and ensures consistency.
• Database servers: Relational (MySQL, PostgreSQL, Microsoft SQL Server) or NoSQL (MongoDB, Cassandra).
• Database Management Systems: Provide tools to create, access, and manage data.
• Storage providers (AWS S3, Azure Blobs, etc)

Separating concerns among these tiers enhances the software’s modularity. This makes updating, maintaining, or replacing specific components easier without breaking the whole application.

3-tier application examples

Whether a desktop or web app, 3-tier applications come in many forms across almost every industry. Here are a few relatable examples of how a 3-tier architecture can be used and a breakdown of what each layer would be responsible for within the system.

E-commerce websites

• Presentation Layer: The online storefront with product catalogs, shopping carts, and checkout interfaces.
• Logic Layer: Handles searching, order processing, inventory management, interfacing with 3rd-party payment vendors, and business rules like discounts and promotions.
• Data Layer: Stores product information, customer data, order history, and financial transactions in a database.

Content management systems (CMS)

• Presentation Layer: The administrative dashboard and the public-facing website.
• LogicLayer: Manages content creation, editing, publishing, and the website’s structure and logic based on rules, permissions, schedules, and configuration
• Data Layer: Stores articles, media files, user information, and website settings.

Customer relationship management (CRM) systems

• Presentation Layer: Web or mobile interfaces for sales and support teams.
• Logic Layer: Processes customer data, tracks interactions, manages sales pipelines, and automates marketing campaigns.
• Data Layer: Maintains a database server with data for customers, contacts, sales opportunities, and support cases.

Online booking platforms (e.g., hotels, flights, appointments)

• Presentation Layer: Search features, promotional materials, and reservation interfaces.
• Logic Layer: Handles availability checks, real-time pricing, booking logic, and payment processing to 3rd-party payment vendors.
• Data Layer: Stores schedules, reservations, inventory information, and customer details.

Of course, these are just a few simplified examples of a 3-tier architecture in action. Many of the applications we use daily will use a 3-tier architecture (or potentially more tiers for a modern web-based application), so finding further examples is generally not much of a stretch. The examples above demonstrate how application functionality can be divided into one of the three tiers.

Benefits of a 3-tier app architecture

One of the benefits of the 3-tier architecture is it’s usually quite apparent why using it would be advantageous over other options, such as a two-tier architecture. However, let’s briefly summarize the advantages and benefits for developers, architects, and end-users who will build or utilize the 3-tier architecture pattern.

Scalability

Each tier can be independently scaled to handle increased load or demand. For example, you can add more servers to the logic tier to improve processing capabilities without affecting the user experience or add more database servers to improve query performance.

Maintainability

Changes to one tier often have minimal impact on the others, making it easier to modify, update, or debug specific application components. As long as contracts between the layers (such as API definitions or data mappings) don’t change, developers can benefit from shorter development cycles and reduced risk.

Flexibility

You can upgrade or replace technologies within individual tiers without overhauling the entire system. This allows for greater adaptability as requirements evolve. For example, if the technology you are using within your data tier does not support a particular feature you need, you can replace that technology while leaving the application and presentation layers untouched, as long as contracts between the layers don’t change (just as above).

Improved Security

Multiple layers of security can be implemented across tiers. This also isolates the sensitive data layer behind the logic layer, reducing potential attack surfaces. For instance, you can have the logic layer enforce field-level validation on a form and sanitize the data that comes through. This allows for two checks on the data, preventing security issues such as SQL injection and others listed in the OWASP Top 10 .

Reusability 

Components within the logic tier can sometimes be reused in other applications, promoting efficiency and code standardization. For example, a mobile application, a web application, and a desktop application may all leverage the same application layer and corresponding data layer. If the logic layer is exposed externally through a REST API or similar technology, it also opens up the possibility of leveraging this functionality for third-party developers to take advantage of the API and the underlying functionality.

Developer specialization 

Teams can specialize in specific tiers (e.g., front-end, back-end, database), optimizing their skills and improving development efficiency. Although many developers these days focus on full-stack development, larger organizations still divide teams based on frontend and backend technologies. Implementing a 3-tier architecture fits well with this paradigm of splitting up responsibilities.

The benefits listed above cover multiple angles, from staffing and infrastructure to security and beyond. The potential upside of leveraging 3-tier architectures is wide-reaching and broadly applicable. It leaves no question as to why 3-tier architectures have become the standard for almost all modern applications. That being said, many times, the current implementation of an application can be improved, and if an application is currently undergoing modernization, how do you ensure that it will meet your target and future state architecture roadmap? This is where vFunction can swoop in and help.

How vFunction can help with modernizing 3-tier applications

vFunction offers powerful tools to aid architects and developers in streamlining the modernization of 3-tier applications and addressing their potential weaknesses. Here’s how it empowers architects and developers:

Architectural observability

vFunction provides deep insights into your application’s architecture, tracking critical events like new dependencies, domain changes, and increasing complexity over time. This visibility allows you to pinpoint areas for proactive optimization and the creation of modular business domains as you continue to work on the application.

Resiliency enhancement

vFunction helps you identify potential architectural risks that might affect application resiliency . It generates prioritized recommendations and actions to strengthen your architecture and minimize the impact of downtime.

Targeted optimization

vFunction’s analysis pinpoints technical debt and bottlenecks within your applications. This lets you focus modernization efforts where they matter most, promoting engineering velocity, scalability, and performance.

Informed decision-making

vFunction’s comprehensive architectural views support data-driven architecture decisions on refactoring, migrating components to the cloud, or optimizing within the existing structure.

By empowering you with deep architectural insights and actionable recommendations, vFunction accelerates modernization architectural improvement processes, ensuring your 3-tier applications remain adaptable, resilient, and performant as they evolve.

In this post, we looked at how a 3-tier architecture can provide a proven foundation for building scalable, maintainable, and secure applications. By understanding its core principles, the role of each tier, and its real-world applications, developers can leverage this pattern to tackle complex software projects more effectively.

Key takeaways from our deep dive into 3-tier applications include:

• Separation of Concerns: A 3-tier architecture promotes clear modularity, making applications easier to develop, update, and debug.
• Scalability: Its ability to scale tiers independently allows applications to adapt to changing performance demands.
• Flexibility: Technologies within tiers can be updated or replaced without disrupting the entire application.
• Security: The layered design enables enhanced security measures and isolation of sensitive data.

As applications grow in complexity, tools like vFunction become invaluable. vFunction’s focus on architectural observability, analysis, and proactive recommendations means that architects and developers can modernize their applications strategically, with complete visibility of how every change affects the overall system architecture. This allows them to optimize performance, enhance resiliency, and make informed decisions about their architecture’s evolution.

If you’re looking to build modern and resilient software, considering the 3-tier architecture or (a topic for another post) microservices as a starting point, combined with tools like vFunction for managing long-term evolution, can be a recipe for success. Contact us today to learn more about how vFunction can help you modernize and build better software with architectural observability.

Principal Architect

Starting from a young age, Michael has loved building things in code and working with tech. His career has spanned many industries, platforms, and projects over the 20+ years he has worked as a software engineer, architect, and leader.

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N-Tier Architecture: Tier 2, Tier 3, and Multi-Tier Explained

When business computing began to move from the mainframe to more affordable commodity machines, one would pick a given computer and “promote” it to server status by installing a database engine, some sort of code interpreter plus compiler, and develop software code that would then create the needed software tool. This meant that the user interface software (UI), the program itself, and the database would be running on the same platform (operating system and computer).

It was not long until the IT industry started realizing that things like distinct patching time frames from operating system and database engine manufacturers, recurrent common incidents, or even the need to update/upgrade components required urgent mitigation by having the processing and database tiers physically and logically split. Thus, Tier 2 architecture solutions started to be utilized.

As the internet became popular in the 1990s, it brought with it a revolution in terms of a user interface which was more performant and capable, but necessitated a specific web server. This widely empowered the proliferation of Tier 3 architecture in which the UI component was separated from the core computing and the database.

The graphic below shows how this plays out on the web:

What is N-Tier Architecture?

Before moving further, it is important to clarify the difference between a “Tier” vs “Layer”. A layer is a logic component within a software suite that accomplishes a given functionality, whereas a tier is the logical and hardware platform where such layer runs.

Most of the time it makes sense to split the above-mentioned tiers to achieve further architecture flexibility, synergy, security, and efficiency.

Consider Amazon.com as an example:

• Amazon needs to be accessible from anywhere, anytime and on any platform (PC; Tablet; Smartphone) so just on the Presentation Tier there are, in fact, several tiers with distinct “flavors” (Windows, iOS, Android).
• The Business Logic Tier itself comprehends not only servers distributed by several geographies processing data, but also automated input from warehouses and logistics components (tiers) that process data by themselves (distinct software layers) to convey information to the Amazon Business Logic Tier (so several tiers here also).
• Finally, the Data Tier is not only replicated and distributed but split as well into distinct levels of data instances (layers) in separate servers (tiers).

An N-Tier Architecture detailed example

Let’s look at a concrete example from the automotive industry concerning logistics software that aims to serve the manufacturer’s assembly line with split second up to date information on parts delivery status, hence needing to be fed by data from:

• The factory shop floor (assembly line) – did the parts arrive or not
• 3 rd party parts supplier companies – were the parts produced
• Logistics warehouses – did the parts leave/arrive at the warehouse
• Trucks on the road – where are they, carrying which parts
• Logistics “control room” – where is everyone and everything
• Factory production forward planning area – which parts do we need, by when, to achieve optimized production cycles

To accomplish this, a system is required that can:

• Constantly collect information from several distinct sources (internal and external/ remote) on the status.
• Then process it and return valuable status information that would enable accurate assertive awareness to decision makers on how progress was being achieved regarding production forecast in a manner that those could act to mitigate any high potential noncompliance risks.
• Allow the forward planning team to issue parts production orders for the following days to comply with the establish production plan.

Below is the system architecture for the necessary software tiers:

Presentation Tier

The presentation tier must address several types of user interface protocols and platforms, in specific:

• The car manufacturer’s internal users, from both the logistics control room and production planning areas where users could make changes to business rules and processes. This requires a robust, secure UI (such as a desktop client application); additionally, key users on the shop floor need to query and check-in parts as they arrive. This would run from a client service software layer on a machine that would be physically within the manufacturer’s network and served by the entire LAN/WAN infrastructure (assuring redundancy, added security, and speed).
• The 3 rd party suppliers and logistics warehouse users reside on 3 rd party entities’ IT landscapes, and are therefore not allowed access to the manufacturer’s LAN or WAN. Therefore, the most suitable, safe and fast solution would be to develop a web based client service software layer resorting to a web server cluster with one machine cluster inside the manufacturer’s data center and another one in the DMZ (where authorized providers can access via strong authentication protocols). Both cluster nodes (internal and DMZ) should be installed in distinct geographies to allow redundancy and high availability.
• The trucks would need to be equipped with automated I/O clients that would convey the GPS coordinates and the material’s list ID via a public mobile web data service through web servers installed on the DMZ via two ISPs from distinct countries to assure redundancy and high availability.
• Some special users, like area managers and plant directors, would need to get alerts and messages to access the system under a management reporting perspective via their smartphones or tablets through centralized web servers inside the manufacturer’s network (two geographies for redundancy assurance) as well as on the go via the ISPs.

Business Logic Tier

The business logic tier would be constituted by several tiers of application server clusters distributed by multiple data centers in separate geographies with a production layer running on one server and a quality/tests layer running on another server in each data center.

The data tier would consist of an active database server cluster with multiple nodes (servers) each running its layer distributed by two data centers in separate geographies plus a historic data/ quick recovery tier at yet another distinct geographic location.

This example assumes the organization is responsible for the entire infrastructure – a cloud-based architecture with virtualized environments would provide even more flexibility, resilience and “Tiers” as well as “Layers” to the entire solution.

Advantages of N-Tier Architecture

• Scalability – having several separated components in the architecture allows easy scalability by upgrading one or more of those individual components. As an example, if the number of public clients grows that may require splitting the Webservice by adding new capacity to deal with the client demand which means more Web Servers on the Presentation Tier; another example would be an online shot that grows its product portfolio, in this case, the need to grow will most likely be in the Data Tier.
• Enhanced Security – An architecture that is distributed by several tiers allows placing those in distinct security zones (both logic as well as geographic) in order to assure that each component is protected according to its core business criticality level. In the presented example, the web servers, although in a firewall-protected DMZ, have less need for security coverage than the application servers or database servers where all critical core business data is being processed or resides.
• Resilience and Redundancy – Critical components can easily be split in tiers that are clustered and geographically split to ensure failover, hence a more resilient system.
• Maintenance flexibility – As with the case of scalability, having distinct tiers allows pin pointed maintenance actions that do not produce collateral unwanted effects. This means that maintenance scheduling has fewer dependencies from 3 rd party components.
• Disaster Recovery – An N-Tier Architecture allows individual components to restore in case of partial service disruption being it severe or not, hence allowing shorter service recovery times. In the case of robust, redundant well-distributed systems (the likes of ones supporting Google, Amazon, PayPal, other) the restore activities are not even noted by end users’ due to the redundancy in place.
• Developer Friendly Environment – Having the several coding layers split by distinct tiers allows developers to focus on their individual task without having to share resources or bear in mind collateral potential impacts in each other’s tasks/ domains. This is the type of architecture that also empowers frameworks and programming cultures like DevOps and Agile/Lean.

Disadvantages of N-Tier Architecture

• Performance – It seems a paradox that having the several components split to allow better efficiency and performance may result in the risk of lower performance. This risk basically pertains to 3 rd party components/services. Having the architecture distributed by distinct geographies and tiers means that the entire system becomes highly dependent on the I/O flow. If within a closed network (a LAN/ WAN) the critical element is the entire cabling, switching and routing infrastructure, whereas in the case of using cloud-based infrastructure the topic additionally consists of several ISPs, who’s individual communication infrastructure may not be synchronous in terms of performance.
• Higher CAPEX and OPEX – adding components to the architecture means the need for additional initial investment, running maintenance expenses budget as well as support services. This is particularly of concern when not relying on cloud-based services.

How N-Tier Has Progressed into The Cloud

Over the last few decades, IT systems have become one of the pillars of our global economy and key factors like security, high availability and flexibility have led most corporations to migrate their core business related IT systems to an N-Tier Architecture.

So, what was the problem? OPEX and CAPEX! Multiplying the number of tiers and software layers within a geographically distributed architecture to assure the above mentioned key factors was not cost effective for most companies, but then … the market responded with robust cloud computing offering.

Companies like IBM or AWS (Amazon Web Services) created large scale computing IT landscapes and companies could now progressively migrate their IT environments to those cloud landscapes while paying merely a fee which represented a small percentage of the cost of implementing and maintaining their own N-Tier Architecture based IT environments.

New strategies for modern service assurance

86% of global IT leaders in a recent IDG survey find it very, or extremely, challenging to optimize their IT resources to meet changing business demands.

These postings are my own and do not necessarily represent BMC's position, strategies, or opinion.

See an error or have a suggestion? Please let us know by emailing [email protected] .

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Stephen Watts

Stephen Watts (Birmingham, AL) contributes to a variety of publications including, Search Engine Journal , ITSM.Tools , IT Chronicles , DZone , and CompTIA .

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Posted on Apr 3

Understanding Layers, Tiers, and N-Tier Architecture in Application Development

In the realm of application development, the architecture of an application significantly impacts its performance, scalability, and ease of maintenance. Developers often talk about "layers" and "tiers" within an application's architecture, terms that are crucial but sometimes misunderstood.

In this article, we will clarify these concepts and delve into the N-tier architecture, focusing on its 3-tier and 4-tier models.

Layers vs. Tiers : What's the Difference?

Although "layers" and "tiers" are often used interchangeably, they refer to different aspects of application architecture:

• Layers are virtual separations within an application that organize its different parts, such as the presentation layer (UI) , the business logic layer , and the data access layer .

These layers exist within the application's code structure and are a logical way to separate responsibilities and functionalities.

• Tiers , on the other hand, refer to the physical distribution of an application's components across different servers or platforms. This physical separation is crucial for an application's scalability, security, and performance. When components are deployed on separate servers and still communicate effectively, they form what is known as a tiered architecture.

Introducing N-Tier Architecture:

N-tier architecture is a scalable and flexible way to structure applications, where "N" represents the number of tiers involved. This architecture divides the application into multiple tiers, each responsible for specific aspects of the application's functionality.

3-Tier Architecture (The Most Common Model):

The 3-tier architecture is a widely adopted model in application development, consisting of the following tiers:

Presentation Tier Tier: This is the user interface (UI) layer, where users interact with the application. It's built using technologies like HTML , CSS , JavaScript , and frameworks like React or Angular .

Application Tier : The core of the application, this layer contains business rules and logic. It acts as an intermediary between the presentation and data access layers, ensuring that user inputs are processed and validated. Technologies used include server-side languages like Java , C# , Python , and frameworks like .NET , Spring , or Django .

Data Tier : This layer is responsible for managing the application's data. This layer handles communication with databases or other storage mechanisms, providing CRUD (Create, Read, Update, Delete) operations. It uses technologies like JDBC, Entity Framework, or ORM.

4-Tier Architecture:

This additional layer abstracts the business logic's external communication, making the system more modular and enabling services to be reused across different parts of the application or even across different applications. It's particularly useful in microservices and service-oriented architectures.

In more complex applications, a 4-tier architecture may be employed, which adds an additional tier:

Delivery Tier : This tier focuses on caching and delivering front-end assets to the client, often through a Content Delivery Network ( CDN ).

The CDN enhances the application's performance and user experience by storing and serving static content from locations closest to the user.

Benefits of N-Tier Architecture:

Scalability : Separating an application into tiers allows for easier scaling of each component independently.

Security : It becomes easier to implement security measures, as each tier can have its own security protocols.

Maintainability : Updates and bug fixes can be carried out more efficiently since changes in one tier do not necessarily affect others.

Efficiency : The development process is streamlined, as developers can focus on specific aspects of the application within each tier.

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Presentation tier

The presentation tier is responsible for interacting with the logic tier through the API Gateway REST endpoints exposed over the internet. Any HTTPS capable client or device can communicate with these endpoints, giving your presentation tier the flexibility to take many forms (desktop applications, mobile apps, webpages, IoT devices, and so forth). Depending on your requirements, your presentation tier can use the following AWS serverless offerings:

Amazon Cognito - A serverless user identity and data synchronization service that enables you to add user sign-up, sign-in, and access control to your web and mobile apps quickly and efficiently. Amazon Cognito scales to millions of users and supports sign-in with social identity providers, such as Facebook, Google, and Amazon, and enterprise identity providers through SAML 2.0.

Amazon S3 with CloudFront - Enables you to serve static websites, such as single-page applications, directly from an S3 bucket without requiring provision of a web server. You can use CloudFront as a managed content delivery network (CDN) to improve performance and enable SSL/TL using managed or custom certificates.

AWS Amplify is a set of tools and services that can be used together or on their own, to help front-end web and mobile developers build scalable full stack applications, powered by AWS. Amplify offers a fully managed service for deploying and hosting static web applications globally, served by Amazon's reliable CDN with hundreds of points of presence globally and with built-in CI/CD workflows that accelerate your application release cycle. Amplify supports popular web frameworks including JavaScript, React, Angular, Vue, Next.js, and mobile platforms including Android, iOS, React Native, Ionic, and Flutter. Depending on your networking configurations and application requirements, you might need to enable your API Gateway APIs to be cross-origin resource sharing (CORS) – compliant. CORS compliance allows web browsers to directly invoke your APIs from within static webpages.

When you deploy a website with CloudFront, you are provided a CloudFront domain name to reach your application (for example, d2d47p2vcczkh2.cloudfront.net ). You can use Amazon Route 53 to register domain names and direct them to your CloudFront distribution, or direct already-owned domain names to your CloudFront distribution. This enables users to access your site using a familiar domain name. Note that you can also assign a custom domain name using Route 53 to your API Gateway distribution, which enables users to invoke APIs using familiar domain names.

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1. What is a 3-Tier Architecture?

2.1 presentation tier, 2.2 application tier, 2.3 data tier, 3. rules in the 3-tier architecture, 4. what are the advantages and disadvantages of using a 3-tier architecture, 5. 3-tier architecture example , 6. a conclusion of the 3-tier architecture.

In the world of software development, 3-tier architecture has become the backbone of modern application design. A 3-tier architecture is an architecture pattern used in applications as a specific type of client-server system. It divides the architecture into three tiers: data layer, application layer, and presentation layer . 

The 3-tier architecture refers to the logical 3-tier system rather than the physical one. It adds a “middle tier” between the client and the database. The main functions and business logic of the system are processed in the middle layer, which is the application layer.

2. The Three Tiers in a 3-Tier Architecture

The presentation tier occupies the top level of the application. It sends content to browsers in web development frameworks, such as CSS, HTML , or JavaScript, and displays information in the form of a graphical user interface (GUI), which allows users to access it directly. It communicates with other layers by putting out the results to the browser and other tiers through API calls. 

The application tier is also called the business logic, logic tier, or middle tier. By processing the business logic for the application, it builds a bridge between the presentation layer and the data layer to make communication faster between the presentation and data layer.

The application tier is usually coded in C#, Java, C++, Python, Ruby, etc.

Data-tier is composed of a persistent storage mechanism and the data access layer. It supports connecting with the database and performing insert, update, delete, and get data from the database based on our input data. 

• The core rule: the presentation layer is only a shell and cannot contain any processing of BizLogic.

2. The design should be from the application layer rather than the presentation layer. The API of the application layer should implement all BizLogic on the API in an object-oriented manner.

3. Whether the data layer is a simple SqlHelper or a class with Mapping, make sure it is independent of the abstract system layer.

4. Whether you’re using COM+( EnterpriseService ), Remoting, or a remote object technology like WebService , whether you’re deploying it on a server or not, you have to consider clustering multiple servers through load balancing in your design.

To sum up, when considering whether a project conforms to the application of a three-tier or multi-tier design, it is necessary to find whether it conforms to the requirements of the project.

Advantages:

• It reduces dependencies between layers, following the principles of 3-tier architecture. Therefore, as long as developers adhere to interface standards and utilize the same entity classes of the object model, it allows different developers to work on each layer. This aspect can significantly improve the development speed of the system.
• In a 3-tier architecture, each layer can be redeveloped or modernized independently, without affecting other layers. This capability shortens the time to market and reduces the cost of integrating new features into software as a service (SaaS), Cloud, and on-premise applications.
• It provides ease of maintenance, and won’t affect other modules, which dramatically reduces maintenance costs and maintenance time.
• Instead of directly accessing the data layer, the presentation layer only connects with the business logic layer, which improves data security.

Disadvantages:

• It reduces system performance. Without a hierarchical structure, businesses could go directly to the database to get the data, but now they have to go through the middle tier.
• The 3-tier architecture sometimes results in cascading changes, especially in the top-down direction. If you need to add a feature in the presentation layer in the context of what is 3-tier architecture, you may need to add code in both the business logic layer and the data access layer to ensure that the design adheres to the principles of 3-tier architecture.

Take FineReport as an example to help you better understand the 3-tier architecture. FineReport is reporting software that adopted the 3-tier architecture. 

The data layer of FineReport is responsible for data management , including data collection, ETL, building a data warehouse, etc. It supports multiple data sources and data integration . 

The application layer of FineReport is responsible for the main functions and business logic. In this part, as an enterprise reporting tool , it supports report design , report generation , and report management. 

In the presentation layer, FineReport can adaptively display reports and dashboards on PC, mobile , and TV screens because the charts in FineReport are developed by HTML5 , which can be used cross-platform, adaptive to web design, and support instant updates.

For example, when you want to create a sales report based on the sales data stored in the CRM, the presentation layers send API calls to the data layer, the data layer of the FineReport runs the query and returns the results to the application layer, which formats it into a web page. The page is then sent back to the browser, where the presentation layer displays the reports on a laptop or other device.

With the 3-tier architecture, you only need to install the designer on the report designer’s computer, and then deploy the project to the server. Other users can directly access the report as long as there is a browser on the computer. 

Once the report requirements change, it is very convenient to design locally and then publish to the remote server by switching the working directory or directly edit the report files on the remote server.

In this way, for companies, it only needs to deploy the project once, and then it can be designed directly and remotely, which makes migrating reports conveniently and improves efficiency.

A 3-tier architecture is an architectural pattern used in the client-server system. Hope you could have a clear understanding of the advantages, disadvantages, rules, and examples of 3-tier architecture after reading this article.

3-tier architecture has revolutionized the software development process by providing developers with a flexible, scalable, and maintainable framework for building modern applications. With the help of powerful reporting tools like FineReport , developers can quickly and easily create complex reports, providing users with the insights they need to make informed decisions.

FineReport provides a free personal-use edition with no limitations and supports up to two concurrent users. For enterprise users interested in pricing and product details, please contact us by clicking the button below:

Also, please feel free to make an appointment for a live demo with our product experts. We will be more clear about your needs and see how FineReport can help you and your organization transform data into value.

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N-tier architecture style

An N-tier architecture divides an application into logical layers and physical tiers .

Layers are a way to separate responsibilities and manage dependencies. Each layer has a specific responsibility. A higher layer can use services in a lower layer, but not the other way around.

Tiers are physically separated, running on separate machines. A tier can call to another tier directly, or use Asynchronous messaging patterns through a message queue. Although each layer might be hosted in its own tier, that's not required. Several layers might be hosted on the same tier. Physically separating the tiers improves scalability and resiliency, but also adds latency from the additional network communication.

A traditional three-tier application has a presentation tier, a middle tier, and a database tier. The middle tier is optional. More complex applications can have more than three tiers. The diagram above shows an application with two middle tiers, encapsulating different areas of functionality.

An N-tier application can have a closed layer architecture or an open layer architecture :

• In a closed layer architecture, a layer can only call the next layer immediately down.
• In an open layer architecture, a layer can call any of the layers below it.

A closed layer architecture limits the dependencies between layers. However, it might create unnecessary network traffic, if one layer simply passes requests along to the next layer.

When to use this architecture

N-tier architectures are typically implemented as infrastructure-as-service (IaaS) applications, with each tier running on a separate set of VMs. However, an N-tier application doesn't need to be pure IaaS. Often, it's advantageous to use managed services for some parts of the architecture, particularly caching, messaging, and data storage.

Consider an N-tier architecture for:

• Simple web applications.
• Migrating an on-premises application to Azure with minimal refactoring.
• Unified development of on-premises and cloud applications.

N-tier architectures are very common in traditional on-premises applications, so it's a natural fit for migrating existing workloads to Azure.

• Portability between cloud and on-premises, and between cloud platforms.
• Less learning curve for most developers.
• Natural evolution from the traditional application model.
• Open to heterogeneous environment (Windows/Linux)
• It's easy to end up with a middle tier that just does CRUD operations on the database, adding extra latency without doing any useful work.
• Monolithic design prevents independent deployment of features.
• Managing an IaaS application is more work than an application that uses only managed services.
• It can be difficult to manage network security in a large system.

Best practices

• Use autoscaling to handle changes in load. See Autoscaling best practices .
• Use asynchronous messaging to decouple tiers.
• Cache semistatic data. See Caching best practices .
• Configure the database tier for high availability, using a solution such as SQL Server Always On availability groups .
• Place a web application firewall (WAF) between the front end and the Internet.
• Place each tier in its own subnet, and use subnets as a security boundary.
• Restrict access to the data tier, by allowing requests only from the middle tier(s).

N-tier architecture on virtual machines

This section describes a recommended N-tier architecture running on VMs.

Each tier consists of two or more VMs, placed in an availability set or virtual machine scale set. Multiple VMs provide resiliency in case one VM fails. Load balancers are used to distribute requests across the VMs in a tier. A tier can be scaled horizontally by adding more VMs to the pool.

Each tier is also placed inside its own subnet, meaning their internal IP addresses fall within the same address range. That makes it easy to apply network security group rules and route tables to individual tiers.

The web and business tiers are stateless. Any VM can handle any request for that tier. The data tier should consist of a replicated database. For Windows, we recommend SQL Server, using Always On availability groups for high availability. For Linux, choose a database that supports replication, such as Apache Cassandra.

Network security groups restrict access to each tier. For example, the database tier only allows access from the business tier.

The layer labeled "Business Tier" in our reference diagram is a moniker to the business logic tier. Likewise, we also call the presentation tier the "Web Tier." In our example, this is a web application, though multi-tier architectures can be used for other topologies as well (like desktop apps). Name your tiers what works best for your team to communicate the intent of that logical and/or physical tier in your application - you could even express that naming in resources you choose to represent that tier (e.g. vmss-appName-business-layer).

Additional considerations

N-tier architectures are not restricted to three tiers. For more complex applications, it is common to have more tiers. In that case, consider using layer-7 routing to route requests to a particular tier.

Tiers are the boundary of scalability, reliability, and security. Consider having separate tiers for services with different requirements in those areas.

Use virtual machine scale sets for autoscaling .

Look for places in the architecture where you can use a managed service without significant refactoring. In particular, look at caching, messaging, storage, and databases.

For higher security, place a network DMZ in front of the application. The DMZ includes network virtual appliances (NVAs) that implement security functionality such as firewalls and packet inspection. For more information, see Network DMZ reference architecture .

For high availability, place two or more NVAs in an availability set, with an external load balancer to distribute Internet requests across the instances. For more information, see Deploy highly available network virtual appliances and this example scenario of High availability and disaster recovery for IaaS apps .

Do not allow direct RDP or SSH access to VMs that are running application code. Instead, operators should log into a jumpbox, also called a bastion host. This is a VM on the network that administrators use to connect to the other VMs. The jumpbox has a network security group that allows RDP or SSH only from approved public IP addresses.

You can extend the Azure virtual network to your on-premises network using a site-to-site virtual private network (VPN) or Azure ExpressRoute. For more information, see Hybrid network reference architecture .

If your organization uses Active Directory to manage identity, you may want to extend your Active Directory environment to the Azure VNet. For more information, see Identity management reference architecture .

If you need higher availability than the Azure SLA for VMs provides, replicate the application across two regions and use Azure Traffic Manager for failover. For more information, see Run Windows VMs in multiple regions or Run Linux VMs in multiple regions .

Related Resources

• N-tier application with Apache Cassandra
• [Windows N-tier application on Azure with SQL Server][n-tier-windows-SQL]
• Microsoft Learn module: Tour the N-tier architecture style
• Azure Bastion
• More information on messaging in an N-tier architecture style on Azure

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Three-Tier Client Server Architecture in Distributed System

Communication in distributed systems.

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In this article, we will get into detail about the three-tier client-server architecture. The most common type of multi-tier architecture in distributed systems is a three-tier client-server architecture. In this architecture, the entire application is organized into three computing tiers

•  Presentation tier
•  Application tier

The major benefit of the three tiers in client-server architecture is that these tiers are developed and maintained independently and this would not impact the other tiers in case of any modification. It allows for better performance and even more scalability in architecture can be made as with the increasing demand, more servers can be added.

What is Three-Tier Architecture?

Three-Tier Architecture is an is an well established software application design pattern which will organizes the application in the three logical and physical computing tiers as following:

Presentation Tier

Application tier, the three tiers in detail.

It is the user interface and topmost tier in the architecture. Its purpose is to take request from the client and displays information to the client. It communicates with other tiers using a web browser as it gives output on the browser. If we talk about Web-based tiers then these are developed using languages like- HTML , CSS , JavaScript.

It is the middle tier of the architecture also known as the logic tier as the information/request gathered through the presentation tier is processed in detail here. It also interacts with the server that stores the data. It processes the client’s request, formats, it and sends it back to the client. It is developed using languages like- Python , Java , PHP, etc.

It is the last tier of the architecture also known as the Database Tier. It is used to store the processed information so that it can be retrieved later on when required. It consists of Database Servers like- Oracle , MySQL, DB2, etc. The communication between the Presentation Tier and Data-Tier is done using middle-tier i.e. Application Tier.

Tier vs. layer

Three-tier application in web development.

Web application will have the same tiers as the three architectures but only difference is that they are with different names.

• Web Server: Web server is an presentation tier of an three-tier architecture which servers as an presentation tier or UI (User Interface) tier. This content can be static or dynamic based on there requirement such as an e-commerce site where users can add products to their shopping cart, enter payment details, or create an account.
• Application Server: Application tier is an middle tier which consists the full logical that is required for the business which will process the user inputs and so on. It will performs the logic’s like queries the inventory database to return product availability or adds details to a customer’s profile.
• Database server: This is back-end tier of an web application it consists all the data so this tier mostly there will be data base such as MySQL, Oracle, DB2 or PostgreSQL.

Other Multi-Tier Architectures

Three Tier Architecture is the widely used for the application development there are some other architecture as mentioned below.

Two-Tier Architecture

This is an fundamental software architecture which consists of two layers or tier one is client and another is server each tier has there own responsibility and they are interlinked with each other or dependent on each other

Client Tier

Client tier is the top most layer which is like an user interface and interaction part of the application. it acts as an web browser, desktop application, or mobile app, through which the user interacts with the application. It is responsible for presenting the data and processing the input of the application.

Server Tier

Server tier is an bottom layer which contains the logic that us required to handle the data processing and data management.

N-Tier Architecture

N-Tier Architecture, also known as Multi-Tier Architecture it divides the application into various number of tiers based on there complexity and requirements. following are the some of the tiers included in the architecture.

• Presentation Tier (Client Tier)
• Application Tier (Middle Tier or Business Logic Tier)
• Data Tier (Data Storage Tier or Database Tier)
• Services Tier (Business Services or Application Services)
• Integration Tier (Integration Services).

Benefits of Three-Tier Architecture

• Logical separation is maintained between Presentation Tier, Application Tier, and Database Tier.
• Enhancement of Performance as the task is divided on multiple machines in distributed machines and moreover, each tier is independent of other tiers.
• Increasing demand for adding more servers can also be handled in the architecture as tiers can be scaled independently.
• Developers are independent to update the technology of one tier as it would not impact the other tiers.
• Reliability is improved with the independence of the tiers as issues of one tier would not affect the other ones.
• Programmers can easily maintain the database, presentation code, and business/application logic separately. If any change is required in business/application logic then it does not impact the presentation code and codebase.
• Load is balanced as the presentation tier task is separated from the server of the data tier.
• Security is improved as the client cannot communicate directly with Database Tier. Moreover, the data is validated at Application Tier before passing to Database Tier.
• The integrity of data is maintained.
• Provision of deployment to a variety of databases rather than restraining yourself to one particular technology.

Disadvantages of Three-Tier Architecture

• The Presentation Tier cannot communicate directly with Database Tier.
• Complexity also increases with the increase in tiers in architecture.
• There is an increase in the number of resources as codebase, presentation code, and application code need to be maintained separately.

FAQs On Three Tier Architecture

1. three tier architecture in dbms.

The database management system (DBMS) is divided into three logical and physical tiers: the presentation tier, the application tier, and the database tier. This is known as three-tier architecture in DBMS.

2. Three Tier Architecture in C#

A C# application is divided into three logical and physical tiers: the presentation tier, the application tier, and the data tier. This is known as three-tier architecture.

3. Three Tier Architecture in AWS(Amazon Web Services)

A Three-Tier Architecture in Amazon Web Services (AWS) refers to the design of web applications or services that utilize AWS cloud resources and services to separate the application into three logical tiers. Each tier has specific responsibilities, and AWS provides a range of services to support the implementation of this architecture.

4. Three Tier Architecture of Mobile Computing

A Three-Tier Architecture in the context of mobile computing refers to the organization of a mobile application or system into three logical tiers or layers, each with specific responsibilities.

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Software Architecture: One-Tier, Two-Tier, Three Tier, N Tier

In this Software Architecture tutorial, we will learn the following

Software Architecture

Software Architecture consists of One Tier, Two Tier, Three Tier, and N-Tier architectures.

A “tier” can also be referred to as a “layer”.

Three layers are involved in the application namely Presentation Layer, Business Layer, and Data Layer. Let’s see each layer in detail:

#1. Presentation Layer

It is also known as the Client layer. The top most layer of an application. This is the layer we see when we use the software. By using this layer we can access the web pages. The main function of this layer is to communicate with the Application layer. This layer passes the information which is given by the user in terms of keyboard actions, mouse clicks to the Application Layer. For example, the login page of Gmail where an end-user could see text boxes and buttons to enter user id, password, and to click on sign-in.

In simple words, it is to view the application.

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#2. Application Layer

It is also known as Business Logic Layer which is also known as the logical layer. As per the Gmail login page example, once the user clicks on the login button, the Application layer interacts with the Database layer and sends required information to the Presentation layer. It controls an application’s functionality by performing detailed processing. This layer acts as a mediator between the Presentation and the Database layer. Complete business logic will be written in this layer.

In simple words, it is to perform operations on the application.

#3. Data Layer

The data is stored in this layer. The application layer communicates with the Database layer to retrieve the data. It contains methods that connect the database and performs required action e.g.: insert, update, delete, etc.

In simple words, it is to share and retrieve the data.

Must Read: Manual Testing Complete Tutorial

Types of Software Architecture:

#1. one tier architecture:.

One Tier application AKA Standalone application

One-tier architecture has all the layers such as Presentation, Business, Data Access layers in a single software package. Applications that handle all the three tiers such as MP3 player, MS Office come under the one-tier application. The data is stored in the local system or a shared drive.

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#2. Two-Tier Architecture:

Two Tier application AKA Client-Server application

The Two-tier architecture is divided into two parts:

1. Client Application (Client Tier) 2. Database (Data Tier)

The client system handles both Presentation and Application layers and the Server system handles the Database layer. It is also known as a client-server application. The communication takes place between the Client and the Server. The client system sends the request to the server system and the Server system processes the request and sends back the data to the Client System

Must Read: SQL for Software Testers Complete Tutorial

#3. Three-Tier Architecture:

Three Tier application AKA Web Based application

The Three-tier architecture is divided into three parts:

1. Presentation layer (Client Tier) 2. Application layer (Business Tier) 2. Database layer (Data Tier)

The client system handles the Presentation layer, the Application server handles the Application layer, and the Server system handles the Database layer.

Note: Another layer is the N-Tier application. N-Tier application AKA Distributed application. It is similar to the three-tier architecture but the number of application servers is increased and represented in individual tiers in order to distribute the business logic so that the logic will be distributed.

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Rajkumar SM is a founder of SoftwareTestingMaterial. He is a certified Software Test Engineer by profession and a blogger & a YouTuber by a choice. He has extensive experience in the field of Software Testing. Furthermore, he loves to be with his wife and a cute little kid 'Freedom'.

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13 comments.

Thanks Amol. Im glad you liked it.

Thank you So much for the information, it is better to add more information about real-life examples for each database architecture.

Thanks for the effort

Thank you for defining it in a way which is easy to understand.

Thanks for your kind words Sushma

Thanks for such an elaborative material. It is good to add knowledge.

Welcome. Keep visiting Galgalo.

Thanks for your effort to explain this. you’ve saved me a lot. Am grateful. blessings.

Thanks for your kind words Emilly Bigz.

Good information about the one tier two tier and three tier application

Thank you for sharing…^_^

Can You describe how the evolution of client-server architecture affects software development processes?

THE INFORMATION IS VERY HELPFUL IN MY IGNOU ASSIGNMENTS.

THANKS A LOT

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A Guide To 3-Tier Architecture

A well-structured and organized solution is crucial for maintainability and scalability in software development. The 3-Tier architecture clarifies concerns, allowing developers to manage the application logic, data access, and presentation layers separately. In this article, we will explore the benefits of this architecture and learn how to implement it in a Visual Studio solution using C#. 

Different Architectures

There are many types of architectures you can use for your applications. You just have to find the one that suits your needs. I like the 3-tier architecture. It’s small, simple, and easy to create. But in some cases, I might change it because of my needs.

There are 9 known architectures we use these days in C#:

• Monolithic architecture
• Microservices architecture
• 3-tier architecture
• Model-View-Controller (MVC) architecture
• Model-View-Presenter (MVP) architecture
• Model-View-ViewModel (MVVM) architecture
• Event-Driven architecture
• Service-Oriented Architecture (SOA)
• Client-Server architecture

I am not going to explain them all. It will become a very large page. But the top 3 popular architectures are:

• Microservices architecture A way to break down a large and complex application into smaller, independent services that are connected. They communicate with each other through APIs. This architecture is becoming popular with bigger projects. You can maintain and deploy the smaller projects more easily.
• 3-tier architecture This type of architecture separates an application into three logical components: the presentation layer, the application layer, and the data layer. This separation of concerns provides better scalability, maintainability, and ease of development.
• Model-View-Controller (MVC) architecture  Well-known if you have created web applications and/or  APIs  with C#. It is a design that separates the application logic from the user interface. The Model component represents the data and the business logic, the View component displays the data, and the Controller component handles user input and updates the Model. This separation of concerns provides a more organized and maintainable codebase.

This tutorial explains the 3-tier architecture mainly because we use this one the most.

The 3-Tier Architecture

This architecture separates the application into three logical components. These three layers help to maintain the code and separation of concern. But for me, it has a different reason I use this architecture: reusability. 

Especially at a time when you might want to create a Windows, macOS, Android, Linux, and iOS app that does the same thing. Do you create the same class over and over again? No, you create a class library with the logic and reference that library in all the projects that need the logic. If something changes in the class library, all other projects get updated.

Three Different Layers

Each layer has its own responsibility but only talks to one other layer. The presentation layer only talks to the application layer and the application layer only talks to the data layer. That means that if you want to show a list of movies, for example, you need to ask the application layer which will ask the data layer. The application layer will send the information of the data layer to the presentation layer. The presentation layer never talks to the data layer directly.

The Data Layer

The first layer I am discussing is the data layer. Maybe the name already tells you what this layer is about: Data. It could be data from a database or a file. Generally speaking, we use this layer to transport data from and to a data source.

This layer does not contain any form of logic. It just sends or retrieves data from the data source. Nothing special. Logic is placed in the application layer.

If you have multiple data sources you need to manage, you can create multiple data layers and bring them together in the application by using dependency injection.

The data layer is a layer that is disappearing a bit. Before we had ORMs, like  Entity Framework , we had to write a lot of code to retrieve and send data from and to a database. With Entity Framework, we don’t need that anymore. That is the reason the logic for the database is moving to the application layer.

The Application Layer

This layer is the beating heart for all your logic. Here you combine logic with the data from the data layer. This layer is responsible for calculations and decisions before sending the data to your presentation layer.

The application layer is often called the business layer. This is a small heritage from the time we had the DLL (data layer library) and the BLL (business layer library). In my projects, I usually call it the business.

For example, the presentation layer requests a list of movies, ordered by title. The application layer will retrieve all the movies from the data layer and sort them by title.

This layer does nothing with the data source directly. The reason is simple: The application layer should never know what kind of data source you use. If you implement dependency injection, the data source can change. Even the whole data layer can change (except for the interface). But the application layer should always be working without changing it.

You can have multiple application layers. I created a logger once. A simple logger that stores messages in a file. But later I needed a logger that stored the messages in a database. I didn’t want two loggers in the single class library representing my application layer. So I created a second application layer for the logger.

It’s usually this layer we  unit test  because it contains the most important code of our application.

The Presentation Layer

And last but not least; the presentation layer. This layer is what a user sees. It could be a console application, WinForms, or an API. It’s the one that gives output that a user or a client application can work with. This layer is also referred to as the top-most layer in this architecture.

It is responsible for presenting the data from the application layer in a user-friendly way. Examples of user-friendly are web pages, WinForms, and mobile apps.

A console application or a WinForms application has a clear GUI. You can click on stuff and it works. An API doesn’t have that. But it does expose JSON (or XML if you want). An API is considered a front-end application.

Conclusion On A Guide to 3-Tier Architecture

The 3-tier architecture is the most used because it’s easy to understand and implement. I encourage you to use this if you just start or create a small project. If you have a really, really small project; make your life easier, and don’t use layers.

The idea behind these layers is to separate data, logic, and application. I think the names are a bit confusing and most people think the application layer is the front end, but that’s the presentation layer. And that is why I call the application layer the business layer.

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Netflix Ad Tier Hits 40M Monthly Active Users, Nearly Double Its Scale At Start Of 2024

Netflix’s 18-month-old advertising tier has nearly doubled in size since the start of 2024, reaching 40 million monthly active users around the world.

The streaming giant revealed the number at its first in-person upfronts presentation in New York. Last year, in a presentation conducted in a virtual format due to the WGA strike, the company said it had 5 million MAUs, and the number grew to 23 million by January.

Netflix President of Advertising Amy Reinhard told the crowd that 40% of all signups now come from the ads plan in countries where it is available. Pricing plays a role in that – at $7 a month, the plan is well below many other services and the company’s own ad-free options. It is also cheaper for an account holder to sign up to a new ad-supported account rather than pay to share their password.

After insisting for years that they would never accept advertising, citing privacy concerns and other factors, Netflix execs hastily announced their reversal on an earnings call in 2022. Microsoft was enlisted as a partner to help ramp up the capability, which reached the market in select territories later that year in a remarkable sprint from first public disclosure to first ad served.

Despite the bumpy start, advertising has come to be embraced by the company (and many bulls on Wall Street) as a key strategic initiative. As it has developed its ad tier, Netflix has also stocked it with live programming, from comedy to award shows to sports. Earlier Wednesday, Netflix and the NFL announced that the streaming giant would carry two Christmas Day games this season, and at least one holiday contest in two seasons after that.

In addition to the stats, Reinhard announced Netflix will launch an in-house ad tech platform. This will give advertisers new ways to buy, new insights to leverage, and new ways to measure impact. 

"Bringing our ad tech in-house will allow us to power the ads plan with the same level of excellence that's made Netflix the leader in streaming technology today," she said.

Chief Content Officer Bela Bajaria unveiled a number of new film and TV titles, but she also spent time giving advertisers a sense of audience engagement. More than 70% of Netflix's ad-supported subscribers watch for more than 10 hours a month, according to Nielsen, a 15% higher level of viewing than the nearest competitor.

“Our audiences are highly engaged - and by engaged I mean that they are choosing to spend their time watching Netflix,” she said. “That's important because engagement is the key to success in streaming. When people watch our shows and movies, they get more value from Netflix, they stick around longer, and they're more likely to recommend us to their friends. And this matters to all of you because you want to be where the audiences are, too.”

Peter Naylor, Vice President of Advertising Sales, closed the presentation on a final, upbeat note. "There's a lot to be excited about over the next year,” he said. “But the story of ads on Netflix this year is pretty simple: It's about growth and momentum."

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