Скачать или смотреть The Traffic Cop of System Design: Load Balancing (L4 vs L7 Explained) Ep. 5

You've scaled your system horizontally by adding more servers (Episode 2). But now you have a new problem: How do you ensure incoming user traffic is spread evenly across them?

If you don't have a plan, one server will get overloaded and crash while the others sit idle. Enter the Load Balancer, the "traffic cop" of your system architecture.

In Episode 5 of our System Design series for freshers, we go deep into Load Balancing. We move beyond the basic definition to cover the critical details interviewers test for: the difference between Layer 4 (Transport) and Layer 7 (Application) load balancing, and the key algorithms used to make routing decisions.

🚀 Catch up on the series:

Ep 2 (Horizontal vs Vertical Scaling):    • What is Scalability? Horizontal Scaling vs...  

Ep 3 (Consistent Hashing):    • Why Simple Hashing FAILS at Scale: Consist...  

Ep 4 (Capacity Estimation):    • System Design Estimation: How to Calculate...  

📘 In this episode, you will learn:

What is a Load Balancer? (The "Traffic Cop" Analogy).

Where does it sit in a typical system architecture?

Hardware vs. Software Load Balancers (e.g., F5 vs. Nginx/HAProxy).

The Critical Difference: Layer 4 (L4) vs. Layer 7 (L7) Load Balancing explained simply.

Key Algorithms Explained:

Round Robin (and Weighted Round Robin)

Least Connections

IP Hash (Session Stickiness)

How Load Balancers handle server failures (Health Checks).

⏱️ Timestamps:
0:00 - Introduction:
The problem with multiple servers
2:15 - What is a Load Balancer? (The Analogy)
4:30 - Where does it fit? (Architecture Diagram)
6:45 - Hardware vs. Software Load Balancers
8:30 - DEEP DIVE: Layer 4 (Transport) Load Balancing
12:00 - DEEP DIVE: Layer 7 (Application) Load Balancing
15:45 - L4 vs. L7 Summary Table
17:00 - Algorithms: Round Robin & Weighted RR
19:30 - Algorithms: Least Connections & IP Hash
21:00 - Summary & Interview Key Takeaways

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#SystemDesign #LoadBalancing #L4vsL7 #Nginx #HAProxy #RoundRobin #SoftwareEngineering #CodingInterview #Freshers2026

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