UNLOCKED CODING

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

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.

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

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

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.

In today’s data-obsessed world, waiting for information is basically a sin. That’s where Kafka steps in — the silent backbone of high-speed, event-driven architecture. It’s not just a message queue; it’s the real-time nervous system for modern apps.

#) Scales effortlessly — handles millions of messages per second.
#) Decouples systems — microservices talk through Kafka instead of shouting at each other directly.
#) Reliable & fault-tolerant — never loses data, even when servers fail.
#) Perfect for streaming — analytics, user activity tracking, IoT data, financial pipelines, you name it.
#) Plays well with everyone — integrates smoothly with Spark, Flink, and any backend with a pulse.

In short: if your product needs real-time insight, event logging, or distributed data flow, Kafka isn’t optional — it’s essential.

🧱 Monolithic Architecture

⚙️ Microservices Architecture

Apply the XYZ method to clearly show impact.
Avoid buzzwords and repetitive phrases.
Include metrics to quantify your achievements.
Highlight what you’ve accomplished, not just responsibility.

1) Check your ATS score.
2) If it’s below 90, refine and update your resume.
3) Use ChatGPT to iteratively improve your LaTeX code and achieve a 92+ ATS score.

AWS S3 (Simple Storage Service) lets you store and retrieve any amount of data from anywhere on the web.
Think of it as your infinite, reliable hard drive in the cloud.

1️⃣ Create a bucket in the AWS console
2️⃣ Upload your files or website build
3️⃣ Set permissions (public/private)
4️⃣ Access via the file’s object URL or API

Static website hosting
Data backups and archiving
App file storage (images, videos, logs)
Integration with CloudFront for CDN delivery.

Docker is a platform that allows developers to build, run, and ship applications inside containers.
Think of containers as lightweight, portable boxes that contain everything your app needs—code, libraries, system tools, and settings.

🔑 Why Docker?
⚡ Consistency → Runs the same everywhere (dev, test, production).
📦 Lightweight → Containers share the host OS kernel (faster than VMs).
🔄 Portability → Deploy apps across different machines/clouds without issues.
🔐 Isolation → Each container runs independently, avoiding conflicts.
🚀 Scalability → Spin up/down containers quickly for microservices & scaling.

🛠 Basic Docker Workflow
1. Write your app code.
2. Create a Dockerfile (instructions for your app image).
3. Build an image → docker build
4. Run a container → docker run

🌍 Where Docker is Used?
Microservices architecture
DevOps & CI/CD pipelines
Cloud deployments (AWS, GCP, Azure)
Local development environments

Learn Docker - https://youtu.be/3c-iBn73dDE

⚡ 1. SSR (Server-Side Rendering)
How it works: Page is generated on every request at the server.
Best for: Dynamic data that changes frequently.
✅ SEO-friendly
❌ Slower than static because server work happens on each request

📦 2. SSG (Static Site Generation)
How it works: Page is built once at build time and reused for all visitors.
Best for: Blogs, docs.
✅ Fastest load (CDN cached)
❌ Needs a rebuild to update data

🔄 3. ISR (Incremental Static Regeneration)
How it works: Pages are statically generated but can be revalidated in the background after a set time.
Best for: News, product catalogs, content that updates occasionally.
✅ Static + fresh content
❌ Delay before updated data appears

💻 4. CSR (Client-Side Rendering)
How it works: Page loads first, then fetches data in the browser using hooks like useEffect.
Best for: User dashboards, data only needed after page load.
✅ Dynamic, no server rebuild needed
❌ Not SEO-friendly (data loads after page render)

⚙️ Multi-Tenant Architecture
A single codebase serves multiple clients (tenants) with data isolation 🔒

1. Shared DB + Shared Schema (tenant_id)
2. Shared DB + Separate Schemas
3. Separate DB per tenant.

🏢 CRM SaaS App →
Company A & B use the same app, different users/data, same infra

🔹 Tenant onboarding & schema isolation
🔹 Role-based auth (RBAC)
🔹 Per-tenant configs & theming
🔹 Tenant billing & usage tracking
🔹 Superadmin dashboard
🔹 Secure API access
🔹 DevOps: CI/CD + Docker + DB migration

🎯 Used in: LMS, HRMS, CRM, CMS, internal tools, etc.