System Design 101: What Happens When You Type a URL?

What actually happens inside the internet when you type google.com and hit Enter?

Welcome to Day 3 of "100 Days, 100 System Design Topics." Today, we are answering the most famous interview question in software engineering history.

On the surface, it looks instant. You type a URL, and a webpage appears. But underneath that simple action lies a complex journey involving DNS resolution, TCP handshakes, SSL/TLS encryption, CDNs, and the browser rendering pipeline.

If you want to understand System Design, you have to understand this flow. It is the connective tissue that links every other concept we will learn in this series—from caching and load balancing to database sharding and latency.

In this video, we break down the 7 critical steps of a web request:

The "Lookups": How the browser checks local caches and asks DNS servers to turn a domain name into an IP address.

The Connection: Understanding the 3-Way TCP Handshake that establishes reliable communication.

The Security: How the TLS handshake encrypts data so no one can snoop on your request (HTTPS vs HTTP).

The Infrastructure: Why your request might hit a CDN (Content Delivery Network) edge server instead of the main backend to save time.

The Processing: How Load Balancers distribute traffic and what happens on the server-side.

The Rendering: How the browser turns raw HTML, CSS, and JavaScript into the pixels you see on the screen.

Whether you are prepping for a tech interview or just want to understand the magic of the internet, this video connects the dots between frontend and backend engineering.

📚 THE "100 DAYS OF SYSTEM DESIGN" SERIES I am documenting my journey through the fundamentals of software architecture. I am breaking down one complex topic every single day.

Day 1: What is a Software System? [Link]

Day 2: Client-Server Architecture [Link]

Day 3: What Happens When You Type a URL? (You are here!)

Full Playlist: https://www.youtube.com/playlist?list=PLK-_t-9JhxPucPLjGwdVmAyWHOZdWheFQ

⏱️ TIMESTAMPS
0:00 - The "Magic" of the Enter Key
0:35 - Step 1: URL Parsing & Local Caching
1:25 - Step 2: DNS Resolution (The Internet's Phonebook)
2:45 - Step 3: The TCP 3-Way Handshake
3:30 - Step 4: HTTPS & The TLS Handshake (Security)
4:20 - Step 5: CDNs & Edge Servers (Speed)
5:15 - Step 6: Backend Processing & Load Balancing
6:00 - Step 7: The Browser Rendering Pipeline (DOM & Paint)
7:10 - Why This Flow Matters for System Design
7:45 - Summary & Recap

🔍 RELATED KEYWORDS System Design Interview Questions, How the Internet Works, DNS Explained, TCP vs UDP, SSL Handshake, Content Delivery Network, Browser Rendering Engine, Critical Rendering Path, Web Performance Optimization, Backend Architecture, Network Protocols, HTTP Requests, Latency vs Throughput.

CONNECT WITH ME Subscribe to follow the 100 Days challenge! If you have a specific topic you want me to cover in the upcoming days, drop a comment below.

#SystemDesign #HowTheInternetWorks #WebDevelopment #BackendEngineering #ComputerScience #TechInterview #DNS #HTTPS #Coding #100DaysOfSystemDesign

Видео System Design 101: What Happens When You Type a URL? канала Async Codex