What is client-server architecture?

Client-server architecture is a way of organizing how applications work over a network, where some devices (clients) request data or services, and others (servers) provide them.

The simplest way to put it: the client asks, the server answers.

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#Who is the client and who is the server

#Client

A client is a program or device that:

• initiates the request
• wants to get data or a service

Examples of clients:

• a browser
• a mobile app
• an email client
• a program that calls an API

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#Server

A server is a program or computer that:

• accepts requests from clients
• processes them
• sends back responses

Examples of servers:

• a web server
• a mail server
• a database server
• an API server

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#How client-server architecture works

A typical scenario:

1. The client sends a request (for example: "give me the web page")
2. The server accepts the request
3. The server processes it (looks up data, checks access)
4. The server sends a response
5. The client shows the result to the user

Important: the client does not know how the server does its work internally, and the server does not care exactly how the client will display the result.

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#Real-life example

When you visit a website:

• the browser is the client
• the website is the server

The browser sends an HTTP request The server returns HTML, CSS, images The browser renders the page

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#Why client-server architecture is used

#Main advantages:

• centralized data (everything is stored on the server)
• easy updates (the server changes, clients keep working)
• security (access control lives on the server)
• scalability (it can serve many clients)

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#What matters for an interview

• Client and server are roles, not necessarily separate computers (one program can be both a client and a server)
• The client always initiates the request
• The server waits for requests and responds to them

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#Short answer for an interview

A convenient phrasing:

Client-server architecture is an interaction model where client applications send requests and servers process those requests and return responses, providing data or services.