Client-server architecture, a short guide

Table of contents

• What is client-server architecture?
• Client and server: roles compared
• 3-tier client server architecture
• Why use a client-server architecture today?
• Practical examples of client-server applications
• Infographic: client-server architecture schema (web/mobile)

When it comes to computer science and online engineering, client-server architecture represents one of the fundamental models on which most modern web applications, websites and digital services are based.

But what is meant by client-server architecture? How does it work? And what advantages does it offer companies compared to other client architectures?

In this article we will delve into the structure, logic and technologies behind client server systems, examining practical examples, use cases and benefits in terms of efficiency, scalability and security.

What is client-server architecture?

Client-server architecture is a communication model between two distinct entities: the client and the server. The client can be a computer, a smartphone or another device with a user interface that makes requests; the server, on the other hand, is a system that runs on a dedicated infrastructure and responds to these client requests , providing data, services or resources.

This “request-response” logic is the basis of how almost every website, web application, or web server works.

Simple example:

When you open a browser and type a URL, your device (the client ) sends a request to the web server, which returns the web pages for you to display.

Client and server: roles compared

To better understand how client-server works, it is useful to analyze the two types of components involved:

Client side

• User interface.
• Requires resources or services.
• It can be a browser, an app, a desktop program.

Server side

• Processes and responds to requests.
• Manages data, security, authentication.
• It runs on an optimized operating system, such as Linux Server or Windows Server.

Client and Server: differences

3-tier client server architecture

Among the various architectural models, the three-tier architecture stands out, an advanced variant of the client-server. Here, each level is logically separated to ensure flexibility, security and easy maintenance.

Structure:

• Presentation (Client)
• It includes the user interface, such as a browser or mobile app.
• Application Logic (Application Server)
• It contains the business rules, the communication between client and server, and the decisions to be processed.
• Data Layer (Database Server)
• Manages data storage and queries.

Advantages:

• Separation of responsibilities.
• Vertical and horizontal scalability.
• Improved security, because each layer can have its own policies.

Technical example (web):

// Client-side AJAX request

fetch('/api/user/123')

.then(response => response.json())

.then(data => console.log(data));

// Intermediate server (logical level)

$userId = $_GET['id'];

$result = getUserFromDB($userId);

echo json_encode($result);

-- Data Layer Query

SELECT * FROM users WHERE id = 123;

Why use a client-server architecture today?

In 2025, adopting a client-server architecture is a strategic choice for many companies. The reasons? Efficiency, reliability and centralization of resources. Let’s look at them in detail.

1. Scalability

A server can serve other clients in parallel. Simply power up the server machine to handle higher loads, for example in an e-commerce.

2. Centralization

Updates, patches, backups and configurations are managed in one place, improving security.

3. Modularity

Thanks to the three-tier architecture, any part of the system can be updated or replaced without affecting the entire ecosystem.

4. Interoperability

Different clients can be supported: browser, mobile app, desktop terminal, IoT.

Practical examples of client-server applications

1. Webmail

Gmail, Outlook, and Yahoo Mail follow the client-server paradigm. The browser sends requests, the server returns emails.

2. Banking Applications

Banking mobile apps rely on REST requests to the web server, which in turn queries databases.

3. Online video games

The game must be fluid and real-time: position and scoring data are managed in real time between client and server.

4. E-commerce

Amazon, Zalando and Shopify use client server systems to manage carts, orders, payments.

Infographic: client-server architecture schema (web/mobile)

In summary

Understanding client-server architecture is not just a technical question, but a real necessity for anyone operating in the digital world. This model continues to be the cornerstone of every modern web application, web server, and website.

Its flexibility, security, and adaptability make it essential for companies of all sizes, and ongoing technological developments — cloud computing, microservices, edge computing — only reinforce its centrality.

Questions and answers

1. What is client-server architecture?
   It is a model where a client sends requests to a server, which responds with data or services.
2. What are the benefits of client-server for businesses?
   Scalability, centralization, security and support for multiple client devices.
3. How does communication between client and server work?
   Through protocols such as HTTP, which handle requests and responses between the two components.
4. What are the differences between client and server?
   The client requests data, the server provides it. They are complementary roles.
5. What is meant by three-level architecture?
   A structure with separate client, application server and data server.
6. Which operating systems support client-server architecture?
   All: Windows, Linux, macOS, Android, iOS, with appropriate configurations.
7. Are there alternatives to client-server architecture?
   Yes, like the peer-to-peer model, but it is less suitable for centralized services.
8. Can the client be a mobile app?
   Yes, as long as it interacts with a server via API or HTTP requests.
9. What are well-known examples of client server systems?
   Gmail, Facebook, Amazon, Spotify, all web and mobile apps.
10. Do you need to know programming languages to implement it?
    Yes, at least one of JavaScript, PHP, Python or Java for the server side and HTML/CSS for the client.