Load Balancing and Traffic Management

Choose the right Azure traffic service based on layer, protocol, and scope: Azure Load Balancer, Application Gateway, Front Door, and Traffic Manager.

What Is It? (Simple Explanation)

Load balancing spreads traffic across healthy backends so one overloaded server does not bring down the application.

Why Do We Need It?

• High availability and fault tolerance.
• Performance under burst traffic.
• Controlled traffic steering across regions and applications.

How It Works (Technical)

Real-world Analogy

Load Balancer is a receptionist assigning visitors to available staff. Traffic Manager is a city-level signboard sending people to different branches.

Visual Representation

Hands-on Commands

# Create public load balancer
az network lb create -g rg-lb -n lb-web --sku Standard --public-ip-address lb-pip --frontend-ip-name fe-web --backend-pool-name be-web

# Create health probe
az network lb probe create -g rg-lb --lb-name lb-web -n probe-http --protocol Http --port 80 --path /

# Create load balancing rule
az network lb rule create -g rg-lb --lb-name lb-web -n rule-http \
  --protocol Tcp --frontend-port 80 --backend-port 80 \
  --frontend-ip-name fe-web --backend-pool-name be-web --probe-name probe-http

Real-world Use Case

An e-commerce platform uses Front Door for global region failover, Application Gateway with WAF for web-layer protection, and internal load balancer for app-tier VM pools.

Debugging Scenario

Issue: Load balancer is up, but backend receives no traffic.

• Check backend pool member health.
• Validate probe path and status code responses.
• Confirm NSG allows probe and client traffic.
• Ensure backend app listens on expected port and interface.

Interview Questions

Summary

Select traffic services based on layer and scope: L4 regional balancing, L7 application routing, or global edge/dns routing. Correct selection is a key architecture decision.