Stop 08 · Systems & Technical UnderstandingTopics · 1/9

How Software Systems Work (Client-Server Basics)

In short

When a user says 'the app is broken', is it their phone, the server or the data? Knowing the basic client-server picture helps you ask the right question and send the bug to the right person.

A basic mental model — the client (app, browser) requests something, the server processes it and responds — enough to understand where a bug or requirement actually lives when discussing it with engineers.

The purple blob passes a paper slip through a small ticket counter window at a railway station.

Think of it like this

The railway enquiry window

You stand at the window and ask, 'Is the Rajdhani running late?' The clerk can't see the train. He checks the central system, reads the answer and tells you. You're the client, the clerk's computer is the server, and the records behind it are the database.

Watch it happen

What happens when you tap 'My orders'

App (client)

Server

Database

GET /my-orders

1/5You tap the button. The app sends a request over the internet to the company's server.

The big ideas

What you need to know

Client = what users touch

The app or browser shows screens and collects input. Layout bugs and offline issues usually live here.

Server = the rules

The server applies business rules like discounts, limits and permissions. Most 'wrong answer' bugs live here.

Database = the memory

Data is stored here. If the data itself is wrong or missing, fixing the screen won't help.

Network in between

Requests travel over the internet. Slow or failing networks cause timeouts that look like app bugs.

Save yourself the pain

Common mistakes

Oops

Writing a requirement like 'the app should calculate the discount'.

Do this instead

Say the rule, not the place. Engineers will usually put rules on the server so every client gets the same answer.

Oops

Logging 'app not working' as a bug.

Do this instead

Say what you tapped, what you expected, what you saw, and on which device and network.

Your mission

Watch requests happen

~15 min

Quick check

Users on Android and iPhone both see the wrong delivery fee. Where is the bug most likely?

Go deeper

1Diagram what happens when a user submits a form, from client to server and back.
2Learn where 'the frontend' and 'the backend' each live in this model.
3Practice explaining this model to someone with no technical background.