Content Delivery Network is a group of geographically distributed servers that work together to provide fast delivery of Internet content.
Instead of every user downloading data from a single central server (which might be halfway across the world), a CDN allows them to download the content from a "local" server near them.
* Goal: Reduce latency (delay) and improve load speeds.
* Key Concept: It moves the content physically closer to the user.

The Flow: How it Works

1) User Request: You type a URL (e.g., e.com/image.jpg) into your browser
2) DNS Resolution: Instead of pointing directly to the main server (Origin), the DNS routes your request to the nearest CDN Edge Server based on your location.
3) Cache Check (Hit vs. Miss):
4) Cache Hit: If the Edge Server already has the image saved, it sends it to you immediately. (Fastest)
5) Cache Miss: If the Edge Server does not have the image, it requests it from the Origin Server, saves a copy for future users, and then sends it to you.

Adaptive Bitrate Streaming is a video delivery technique where the player dynamically switches video quality based on your network speed, device, and buffer health. Translation: instead of freezing dramatically at 99%, it quietly drops from 1080p to 720p and keeps going.

How it works
1. Encoding
The same video is encoded at multiple bitrates and resolutions.
Example: 240p, 360p, 720p, 1080p.
2. Chunking
Each version is split into small segments (2–10 seconds).
3. Manifest file
A playlist describes all available qualities and segment URLs.
Think of it as a menu, not the food.
4. Smart player logic
The player constantly checks:
Current bandwidth
Buffer level
CPU / device capability
Then it picks the best possible segment right now.

Common ABR protocols
MPEG-DASH
HTTP Live Streaming (HLS)

Project
Video Player with multiple quality options (adaptive bitrate streaming)
Frontend: React.js or Next.js
Backend: Node.js or Go
Transcoding: FFmpeg Cron jobs
Storage: Amazon S3 or Cloudflare R2
CDN: Cloudflare

WEB WORKER

A Web Worker lets JavaScript run in the background, on another thread, so your main UI thread can keep doing its job.

Why they exist

JavaScript in the browser is single-threaded.

So when you do heavy work:-The page dies. Gracefully.
Web Workers fix this by moving heavy work off the main thread.

Can Do

Heavy calculations
Encryption / decryption
Video processing
Anything CPU-intensive

❌ Cannot do

Access DOM
Touch window, document, alert
Directly modify UI

Data is copied or transferred, not shared (unless using SharedArrayBuffer)

Types of Web Workers

1.Dedicated Worker
One page → one worker (most common)
2. Shared Worker
Multiple tabs → one worker
Rare. Slightly cursed.
3. Service Worker
Offline, caching, push notifications

Real-world usage

Video players (HLS, DASH)
Crypto / hashing
Image processing
Large JSON parsing
CAPTCHA behavior analysis
Analytics that should not freeze UI

1. Content Encryption
Media is split (DASH/HLS) and encrypted using AES (128/CTR) with a Content Encryption Key (CEK).

2. Packaging & Metadata
Manifests (MPD/M3U8) carry DRM data like KIDs and PSSH to identify the DRM system.

3. Playback Initialization
The client detects encrypted media and loads a CDM via EME. JavaScript never sees keys.

4. License Request
The CDM sends a license challenge with device info, KIDs, and nonces to the server.

5. License Response
The server validates access and returns encrypted CEKs with usage rules, signed.

6. Secure Decryption
Keys decrypt inside secure hardware (TEE). Plain media never enters normal RAM.

7. Output Protection
Decrypted frames use secure paths to display. HDCP blocks external capture.

What is a Role-Based System?

A Role-Based Access Control (RBAC) system is a way to control who can do what in an application.
Assign roles (like Admin, User, Editor) Each role has permissions Users get access based on their role

🎯 Example
Admin → Can create, edit, delete users
Editor → Can edit content
User → Can only view content
🔁 How It Works (Step-by-Step)
1. User logs in
2. System checks their role
3. Based on role → allows or blocks actions

🔐 Real-Life Usage: Admin panels, Banking apps, School portals, Company dashboards

expected salary - 9k intern, 32k Fresher

Full Stack Project Ideas

Beginner → Intermediate

Intermediate → Advanced

Advanced → Very Hard