AWS: Elastic Load Balancing

Understanding AWS Elastic Load Balancing (ELB): ALB (L7), NLB(L4), and GLB(L3)

Elastic Load Balancing (ELB) in AWS is a powerful service that automatically distributes incoming application traffic across multiple targets and virtual appliances in one or more Availability Zones (AZs).

Here’s an in-depth look at the three main types of load balancers offered by AWS: Application Load Balancer (ALB), Network Load Balancer (NLB), and Gateway Load Balancer (GLB).

Application Load Balancer (ALB)

What is ALB?

ALB operates at the Layer 7 (Application layer) and is designed to handle HTTP/HTTPS traffic. It offers advanced routing, SSL termination, and WebSocket support, making it suitable for web applications.

Use Cases:

  1. E-commerce Websites: Securely routing user requests based on browsing behavior.
  2. Content Management Systems (CMS): Directing requests to appropriate servers for images, videos, or text.
  3. Mobile Applications: Managing user sessions and data-specific routing.
  4. Microservices Architecture: Distributing requests among microservices.
  5. API Gateways: Routing API requests to backend services.

Network Load Balancer (NLB)

What is NLB?

NLB operates at Layer 4 (Transport layer), managing TCP/UDP traffic with ultra-low latency and high throughput. It supports millions of requests per second with minimal latency, ideal for real-time applications.

Use Cases:

  1. Real-time Gaming: Handling low-latency connections for multiplayer games.
  2. High-frequency Trading: Ensuring fast, reliable financial transactions.
  3. VoIP Services: Managing voice over IP connections with low latency.
  4. Video Streaming: Delivering live or on-demand content efficiently.
  5. IoT Applications: Managing numerous concurrent device connections.

Gateway Load Balancer (GLB)

What is GLB?

GLB operates at Layer 3 (Network layer) and is designed to deploy, scale, and manage third-party virtual appliances. It integrates security appliances, scales elastically, and manages network traffic efficiently.

Use Cases:

  1. Network Security Appliances: Integrating firewalls and intrusion detection systems.
  2. Traffic Inspection: Routing traffic through security appliances for deep inspection.
  3. Advanced Network Monitoring: Using analytics tools to monitor traffic.
  4. Compliance Solutions: Ensuring data meets regulatory standards.
  5. Hybrid Cloud Architectures: Managing traffic between on-premises and cloud environments.

Why Different Load Balancers?

Each load balancer type caters to specific application requirements, traffic types, and performance needs. ALB is perfect for web applications needing intelligent routing and security, NLB is ideal for high-performance, low-latency applications, and GLB is best for integrating network security solutions.


AWS Elastic Load Balancing (ELB) provides flexible, scalable, and robust solutions to manage diverse application traffic efficiently. Whether you need sophisticated routing, low latency, or integrated security, AWS offers a suitable load balancer to meet your requirements. Leveraging ELB ensures high availability, improved performance, and seamless scalability across multiple Availability Zones.

For more information, you can explore AWS’s official documentation.