Load Balancer: Key Role, Functions, and Algorithms in Modern Infrastructure

A load balancer is a networking component that distributes incoming application or network traffic across multiple backend servers to ensure high availability, performance, and fault tolerance. It prevents server overload, reduces latency, and keeps applications responsive even during peak usage.
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Load balancers are widely used in cloud, microservices, and distributed system architectures to provide scalability, reliability, and efficient traffic control.

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How Load Balancers Operate

Load balancers route requests based on rules and balancing strategies and may operate at different OSI levels:
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• Layer 4 (Transport Layer):
  Routes traffic using TCP/UDP ports and IP addresses; fast and efficient.
  
  
• Layer 7 (Application Layer):
  Routes traffic based on HTTP headers, cookies, or request paths—ideal for content-based routing and modern web applications.
  
  

Load balancers can be implemented as hardware appliances, software instances, or fully managed cloud services (e.g., AWS ELB, Azure Load Balancer, GCP GLB).

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Core Functions

Traffic Distribution

Balances requests across servers based on an algorithm to maintain performance and efficient resource use.

Health Checks & Failover

Monitors backend servers and routes traffic only to healthy instances.

Session Persistence (Sticky Sessions)

Ensures requests from the same client continue to reach the same server when required (e.g., shopping carts, authentication).

SSL/TLS Termination

Decrypts HTTPS traffic at the load balancer to reduce overhead on backend servers.

Global Traffic Management

Directs users to the nearest or most optimal region for reduced latency in multi-region deployments.

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Common Load Balancing Algorithms

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Practical Example

A global streaming platform uses a load balancer to:
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• Route users to the nearest regional servers
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• Terminate SSL at the edge
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• Automatically bypass unavailable instances
  
  

This ensures fast streaming, minimal buffering, and uninterrupted service at scale.

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Related Terms

• Reverse Proxy
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• API Gateway
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• API Integration