1. Starting Point: The User Opens the App

When a user opens the Instagram app or website, they are interacting with the front end. This is everything the user can see—buttons, images, text boxes, and animations. It’s built using web technologies like HTML (structure), CSS (style), and JavaScript (behavior). At this point, the app hasn’t done anything complex; it’s just showing the user interface on the screen.

2. User Login: Entering and Sending Credentials

The user enters their username and password on the login page. When they click the login button, the front end takes this information and sends it to the backend using something called an API request. This communication happens over HTTPS, which encrypts the data to make sure no one can read it while it’s being sent over the internet.

3. Backend Processing: Checking Login Credentials

The backend is the part of the system the user never sees. It lives on servers and handles all the behind-the-scenes logic. Once it receives the login request, it checks the username and password by comparing them to what’s stored in the database. But Instagram doesn’t store your real password. Instead, it stores a hashed version, which is a scrambled version that can’t be easily reversed. When you log in, the backend hashes the password you typed and compares it to the saved one. If they match, you’re allowed in.

4. Database: Where the Data Lives

The database stores all kinds of information—user profiles, posts, messages, comments, likes, and more. It’s like a digital filing cabinet. Every time you do something like upload a photo or like a post, the front end sends a request to the backend, which then updates the database accordingly. The database is protected and only accessible through the backend, so users can’t directly see or change what’s in it.

5. After Login: Viewing Feed and Using the App

Once logged in, the backend sends back an authentication token, which proves to the app that you’re verified. The front end uses this token to request your home feed. Each time you scroll, like a post, or comment, your actions are turned into API requests that go through the backend and touch the database as needed.

6. Security: Protecting Your Information

Instagram uses multiple layers of protection. First, HTTPS keeps your data encrypted while it’s traveling between your phone and the servers. Second, password hashing makes sure your real password is never saved. Third, tokens reduce the need to send your password again and again. On top of that, the backend enforces permissions to make sure users only access what they’re allowed to. Admins, for example, have more access than regular users, and everything is logged and monitored to catch suspicious behavior.

In Summary

Every time you open Instagram and log in, you’re triggering a series of interactions: the front end collects your input, the backend handles the logic and security, and the database stores and retrieves your data. These three parts work together in real time to create the smooth experience you expect—all while making sure your information stays safe behind the scenes.