What is Azure Load Balancer and why is it used?

Updated Feb 20, 2026

Short answer

Azure Load Balancer is a service that distributes incoming network traffic across multiple servers to improve availability, performance, and reliability.

Deep explanation

Azure Load Balancer works at the transport layer (Layer 4) and distributes traffic based on IP address and port number.

It ensures:

No single server becomes overloaded
High availability of applications
Fault tolerance in case one server fails

Types of Load Balancer:

Public Load Balancer → handles internet traffic
Internal Load Balancer → used within private networks

Key functions:

Health monitoring of backend servers
Automatic redirection of traffic
Supports scaling applications horizontally

Real-world example

An e-commerce website runs on 3 Azure Virtual Machines:

When users access the website:

Load Balancer distributes requests evenly
If VM2 crashes, traffic is automatically redirected to VM1 and VM3

This ensures the website stays online without downtime.

Common mistakes

- Thinking Load Balancer stores data or runs applications
- Confusing it with Application Gateway (Layer 7 vs Layer 4)
- Assuming it improves application speed directly
- Ignoring health probe configuration

Follow-up questions

What is the difference between Load Balancer and Application Gateway?
What is health probe in Azure Load Balancer?
What is traffic routing in cloud systems?
Can Load Balancer work across regions?